Document:

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                                                                     EXHIBIT 4.3

                                [EXECUTION COPY]

                    WARRANT AND REGISTRATION RIGHTS AGREEMENT

                                     BETWEEN

                       CORNERSTONE PROPANE PARTNERS, L.P.

                                       AND

                            NORTHWESTERN CORPORATION

                            Dated as of June 30, 2000

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                    WARRANT AND REGISTRATION RIGHTS AGREEMENT

         THIS WARRANT AND REGISTRATION RIGHTS AGREEMENT ("THIS WARRANT
AGREEMENT") is made as of June 30, 2000, by and between CORNERSTONE PROPANE
PARTNERS, L.P., a Delaware limited partnership (the "COMPANY"), and NORTHWESTERN
CORPORATION, a Delaware corporation ("NOR").

                                    RECITALS:

         A.       The Company has requested NOR to enter into a certain
Guaranty Agreement to be executed and delivered effective as of the date
hereof (the "GUARANTY AGREEMENT"), pursuant to which NOR has agreed with Bank
of America, N.A., as agent for lenders, to guarantee up to $40,000,000
principal amount of secured bank debt of Cornerstone Propane, L.P., an
affiliate of the Company, under a Refunding Credit Agreement dated as of
November 20, 1998, as the same has been and may be amended, restated,
supplemented or otherwise modified from time to time (the "CREDIT AGREEMENT").

         B.       As provided in that certain Commitment Letter dated June
30, 2000 between the Company and NOR (the "COMMITMENT LETTER"), and in order
to induce NOR to enter into the Guaranty Agreement, the Company has agreed to
enter into this Agreement.

         NOW, THEREFORE, the parties hereto agree as follows:

                  SECTION 1.   DEFINITIONS.

                  (a) CERTAIN DEFINITIONS. For the purposes of this Agreement,
the following terms have the meanings set forth below:

                  "AFFILIATE" has the same meaning as in Rule 12b-2 promulgated
under the Exchange Act.

                  "BUSINESS DAY" means any day which is neither a Saturday or
Sunday nor a legal holiday on which banks are authorized or required to be
closed in New York, New York, Los Angeles, California or Sioux Falls, South
Dakota.

                  "CLOSING DATE" means August 2, 2000.

                  "COMMON UNITS" means limited partnership interests of the
Company defined as "Common Units" in the Partnership Agreement and having the
rights and obligations specified with respect to Common Units in the Partnership
Agreement.

                  "COMPANY" is defined in the Preamble.

                  "CREDIT AGREEMENT" is defined in the Recitals.

                  "EXCHANGE ACT" means the Securities Exchange Act of 1934, as
amended.

                  "EXERCISE PRICE" means the exercise price per Warrant, which
initially is $0.10 per Common Unit, subject to adjustment from time to time in
accordance with this Agreement.
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                  "FAIR MARKET VALUE PER UNIT" means the arithmetic mean of the
closing sales prices of a Common Unit of the Company as reported by the New York
Stock Exchange Composite Transactions for each of the five trading days
immediately preceding the date of determination or, if not so trading, the fair
value as determined in good faith by the General Partner.

                  "GAAP" means generally accepted accounting principles in
effect from time to time in the United States.

                  "GENERAL PARTNER" means Cornerstone Propane GP, Inc., the
Managing General Partner of the Company, or any successor as Managing General
Partner of the Company.

                  "GOVERNMENTAL AUTHORITY" means any nation or government, any
state or other political subdivision thereof and any entity exercising
executive, legislative, judicial, regulatory or administrative functions of or
pertaining to government.

                  "GUARANTY AGREEMENT" is defined in the Recitals.

                  "HOLDER" means NOR or any subsequent holder of Warrants or
Warrant Units, to which the Warrants or Warrant Units are transferred in
accordance with the provisions of this Agreement.

                  "PARTNERSHIP AGREEMENT" means the Amended and Restated
Agreement of Limited Partnership of Cornerstone Propane Partners, L.P. dated as
of December 17, 1996, as the same has been and may be amended, restated,
supplemented or otherwise modified from time to time.

                  "PERSON" means any natural person, corporation, partnership,
limited liability company, firm, association, trust or any other entity, whether
acting in an individual, fiduciary or other capacity.

                  "PIK UNITS" means Common Units, if any, issued to NOR as
contemplated by the Commitment Letter or otherwise in payment of interest, fees
or other charges payable by the Company to NOR in respect of advances made by
NOR pursuant to the Guaranty Agreement or other credit support furnished by NOR
for the benefit of the Company from time to time.

                  "RULE 144" means Rule 144 promulgated by the SEC under the
Securities Act.

                  "SEC" means the United States Securities and Exchange
Commission.

                  "SECURITIES ACT" means the Securities Act of 1933, as amended.

                  "TERMINATION DATE" is defined in SECTION 6.

                  "WARRANT CERTIFICATES" means the certificates evidencing the
Warrants in the form of EXHIBIT A-1 attached hereto.

                  "WARRANT UNITS" means the Common Units issued upon exercise of
a Warrant by the Holder thereof, together with any other securities which such
Holder may be issued in respect of any such securities, including, without
limitation, by way of any dividend or other distribution on such securities, any
split-up of such securities or a recapitalization, merger, consolidation, share
exchange, reorganization
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or other transaction or series of related transactions in which such securities
are changed into or exchanged for securities of another limited partnership,
limited liability company or corporation.

                  "WARRANTS" means the 381,875 warrants to purchase one Common
Unit of the Company each (I.E., an aggregate of 381,875 Common Units) issued to
NOR on the Closing Date pursuant to this Agreement, and each warrant issued in
substitution or exchange therefor, or in subsequent substitutions or exchanges,
which warrants shall be subject to adjustment and shall have the rights,
privileges and limitations set forth in this Agreement.

                  SECTION 2. ISSUANCE AND EXERCISE OF WARRANTS.

         (a)      The Company agrees that it shall issue and deliver to NOR on
                  the Closing Date Warrant Certificates evidencing in the
                  aggregate 381,875 Warrants, each dated the Closing Date and
                  registered in such name or names as NOR may specify by timely
                  written notice to the Company (it being understood that in the
                  absence of such specification the Company shall issue and
                  deliver to NOR a single Warrant Certificate evidencing 381,875
                  Warrants in the name of NOR). A Warrant may be exercised by
                  NOR or any other Holder only in accordance with the terms and
                  conditions of this Agreement and at any time during the period
                  beginning on the date on which such Warrant becomes
                  exercisable pursuant to SECTION 2(b) hereof and ending on the
                  Termination Date.

         (b)      Each of the 381,875 Warrants shall be immediately exercisable
                  on the date of issuance.

         (c)      Subject to the terms and conditions hereof, Warrants that are
                  exercisable in accordance with this SECTION 2 may be exercised
                  pursuant to this SECTION 2 upon surrender to the Company at
                  its office designated for such purpose (the address of which
                  is set forth in SECTION 13) of the Warrant Certificate or
                  Certificates evidencing the Warrant(s) to be exercised and
                  upon payment to the Company of the aggregate Exercise Price
                  for the number of Warrants which are then exercised. Upon such
                  surrender of Warrant Certificates and payment of the Exercise
                  Price in cash or by check payable to the Company in
                  immediately available funds, the Company shall issue and cause
                  to be delivered with all reasonable dispatch (and in any event
                  within ten Business Days after such surrender and payment) to
                  or upon the written order of the Holder, and registered in the
                  name of the Holder or as it may otherwise specify, a
                  certificate or certificates for the number of full Warrant
                  Units issuable upon the exercise of such Warrants, together
                  with such other property (including cash) and securities as
                  may then be deliverable upon such exercise, including cash for
                  fractional Warrant Units as provided in SECTION 11, PROVIDED
                  that all such Warrant Units shall be subject to the
                  restrictions set forth in SECTION 5 of this Agreement. Such
                  certificate or certificates shall be deemed to have been
                  issued and the Person so named therein shall be deemed to have
                  become a holder of record of such Warrant Units as of the date
                  of the surrender of such Warrant Certificates.

         (d)      Subject to the terms and conditions hereof, the Warrants shall
                  be exercisable at the election of the Holders thereof, either
                  in full or from time to time in part, and in the event that a
                  Warrant Certificate is exercised in respect of fewer than all
                  of the Warrants evidenced by such Warrant Certificate at any
                  time prior to the Termination Date, a new Warrant Certificate
                  evidencing the remaining Warrant or Warrants will be issued
                  and delivered pursuant to the provisions of this SECTION 2(d).
                  All Warrant Certificates surrendered upon exercise of Warrants
                  shall be canceled. The Company shall keep
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                  copies of this Agreement and any notices received hereunder
                  available for inspection during normal business hours at its
                  office. The Company will furnish, at its expense, copies of
                  this Agreement and all such notices, upon request, to any
                  Holder of any Warrant Certificates.

                  SECTION 3. ADJUSTMENT OF EXERCISE PRICE AND NUMBER OF WARRANT
UNITS ISSUABLE. The Exercise Price and the number of Warrant Units issuable upon
the exercise of each Warrant are subject to adjustment from time to time upon
the occurrence of any of the events enumerated in this SECTION 3.

         (a)      ADJUSTMENT FOR CHANGE IN PARTNERSHIP INTERESTS OF THE COMPANY.
                  If the Company (i) makes a distribution on its Common Units
                  payable in any class of its partnership interests, (ii)
                  subdivides its outstanding Common Units into a greater number
                  of units, (iii) combines its outstanding Common Units into a
                  smaller number of units, (iv) makes a distribution on its
                  Common Units in units of its partnership interests other than
                  Common Units, or (v) issues to holders of its Common Units by
                  reclassification of its Common Units any other partnership
                  units, then the number of units for which any Warrant may be
                  exercised in effect immediately prior to such action shall be
                  proportionately adjusted so that the Holder of any Warrant
                  thereafter exercised may receive the aggregate number and kind
                  of partnership interests of the Company which it would have
                  owned immediately following such action if such Warrant had
                  been exercised immediately prior to such action. Such
                  adjustment shall be made successively whenever any event
                  listed above shall occur, and shall become effective
                  immediately after the record date in the case of a
                  distribution and immediately after the effective date in the
                  case of a subdivision, combination or reclassification. If
                  after an adjustment made pursuant to the second preceding
                  sentence a Holder of a Warrant upon exercise of such Warrant
                  may receive partnership interests of two or more classes of
                  partnership interests of the Company, the General Partner of
                  the Company shall determine in the good faith exercise of its
                  reasonable business judgment the allocation of the adjusted
                  Exercise Price between the classes of partnership interests.
                  After such allocation, the exercise privilege and the Exercise
                  Price of each class of partnership interests shall thereafter
                  be subject to adjustment on terms comparable to those in this
                  SECTION 3.

         (b)      REORGANIZATION OF THE COMPANY. In the event of any capital
                  reorganization, recapitalization or reclassification of the
                  partnership interests of the Company, or consolidation or
                  merger of the Company with another entity in which the Company
                  does not continue as the surviving partnership or, if it does
                  so continue, its Common Units do not remain outstanding, any
                  acquisition of all of the outstanding Common Units of the
                  Company by means of a unit exchange, or the sale, lease,
                  transfer, conveyance or other disposition of all or
                  substantially all of its assets to another entity, then, as a
                  condition of and concurrently with such reorganization,
                  recapitalization, reclassification, consolidation, merger,
                  unit exchange or sale, lease, transfer, conveyance or other
                  disposition, lawful and adequate provision shall be made
                  whereby the Holders of the Warrant Certificates shall
                  thereafter have the right to purchase and receive, on the
                  basis and upon the terms and conditions specified in this
                  Agreement and in lieu of the Warrant Units immediately
                  theretofore purchasable and receivable upon the exercise of
                  the rights represented by the Warrants, such units,
                  partnership interests, securities, cash or property as would
                  have been issued or payable with respect to or in exchange for
                  the number of Warrant Units purchasable and receivable
                  immediately prior to such transaction upon the exercise of the
                  rights represented by the Warrant Certificates if such Warrant
                  Certificates
<PAGE>

                  had been exercised immediately prior to such transaction. In
                  any such case appropriate provision shall be made with respect
                  to the rights and interests of the Holders of the Warrants to
                  the end that the provisions of this Agreement (including,
                  without limitation, provisions for adjustment of the Exercise
                  Price and of the number and type of securities purchasable
                  upon the exercise of the Warrants) shall thereafter be
                  applicable, as nearly as may be, in relation to any units,
                  partnership interests, securities, cash or property thereafter
                  deliverable upon the exercise of the Warrants. The Company
                  shall not effect any such consolidation, merger, share
                  exchange or sale, lease, transfer, conveyance or other
                  disposition unless prior to or simultaneously with the
                  consummation thereof the successor entity (if other than the
                  Company) resulting from such consolidation or merger, unit
                  exchange or the entity purchasing or otherwise acquiring such
                  assets or units (i) shall assume by a supplemental Warrant
                  Agreement, reasonably satisfactory in form, scope and
                  substance to the Holders (which shall be mailed or delivered
                  to the Holders of the Warrants at the last address of such
                  Holders appearing on the books of the Company) the obligation
                  to deliver to such Holders such units, partnership interests,
                  securities, cash or property as, in accordance with the
                  foregoing provisions, such Holders may be entitled to purchase
                  (the "SUBSTITUTE SECURITIES") and (ii) shall assume all of the
                  other obligations of the Company set forth in this Agreement,
                  including, without limitation, those under SECTION 23, which
                  shall apply to such Substitute Securities MUTATIS MUTANDIS.
                  Following such assumption such obligations shall apply to the
                  Substitute Securities rather than to the Warrant Units. If the
                  issuer of securities deliverable upon exercise of Warrants
                  under the supplemental Warrant Agreement is an Affiliate of
                  the formed, surviving, transferee or lessee entity, such
                  issuer shall join the supplemental Warrant Agreement. The
                  foregoing provisions of this paragraph shall similarly apply
                  to successive reorganizations, recapitalizations,
                  reclassifications, consolidations, mergers, share exchanges,
                  sales, leases, transfers, conveyances or other dispositions.

         (c)      CERTAIN OTHER DISTRIBUTIONS. If at any time or from time to
                  time the Company shall take a record of the holders of its
                  Common Units for the purpose of entitling them to receive any
                  distribution of

                                    (i) cash (other than a cash distribution
                           payable out of earnings or earned surplus legally
                           available therefor, to the extent, but only to the
                           extent, that the aggregate of all such distributions
                           paid or declared after June 30, 2000 does not exceed
                           the net income of the Company earned subsequent to
                           that date determined in accordance with GAAP), or

                                    (ii) any evidence of indebtedness (other
                           than convertible securities), any of its units or
                           partnership interests (other than Common Units) or
                           any other securities or property of any nature
                           whatsoever (other than cash), or

                                    (iii) any warrants or rights to subscribe
                           for or to purchase any evidences of its indebtedness
                           (other than convertible securities), any of its units
                           or partnership interests (other than Common Units) or
                           any other securities or property of any nature
                           whatsoever,

                  then lawful and adequate provision shall be made whereby the
                  Holders of the Warrant Certificates shall thereafter have the
                  right to exercise the rights represented by the Warrants and
                  to receive upon such exercise (A) such number of Warrant Units
                  as would have been purchasable and receivable immediately
                  prior to the taking of such record
<PAGE>

                  upon the exercise of the rights represented by the Warrant
                  Certificates if such Warrant Certificates had been exercised
                  immediately prior to the taking of such record, and (B) such
                  cash, evidences of indebtedness, units, partnership interests,
                  securities, or other property as would have been distributed
                  with respect to such number of Warrant Units if the same had
                  been held by such Holders on the date of the taking of such
                  record.

         (d)      ISSUANCE OF ADDITIONAL COMMON UNITS. If at any time or from
                  time to time the Company shall (except as hereinafter
                  provided) issue additional Common Units for a consideration
                  less per unit than the Fair Market Value Per Unit in effect
                  immediately prior to issuance of such additional Common Units,
                  then the number of Warrant Units issuable upon exercise of a
                  Warrant shall be adjusted to that number obtained by
                  multiplying the number of Warrant Units issuable upon exercise
                  of a Warrant immediately prior to such adjustment by a
                  fraction the numerator of which shall be the number of Common
                  Units outstanding immediately prior to the issuance of such
                  additional Common Units plus the number of additional Common
                  Units so issued, and the denominator of which shall be the
                  number of Common Units outstanding immediately prior to the
                  issuance of such additional Common Units plus the number of
                  additional Common Units which the aggregate consideration paid
                  for the total number of such additional Common Units so issued
                  would purchase at the Fair Market Value Per Unit in effect
                  immediately prior to issuance of such additional Common Units.
                  The date as of which Fair Market Value Per Unit shall be
                  determined for purposes of this SECTION 3(d) shall be the
                  earlier of the date on which the Company enters into a firm
                  contract for the issuance of such additional Common Units, and
                  the date of actual issuance thereof. This SECTION 3(d) shall
                  not apply to any issuance of Additional Common Units for which
                  an adjustment is made pursuant to the foregoing SECTION 3(a)
                  or as to any issuance pursuant to exercise of warrants or
                  other rights, or conversion of convertible securities, with
                  respect to which an adjustment has previously been made
                  pursuant to SECTION 3(e) upon issuance of such warrants,
                  rights or convertible securities, as the case may be, or any
                  warrants or other rights to obtain the same. No adjustment
                  shall be required pursuant to this SECTION 3(d) with respect
                  to any issuance of additional Common Units pursuant to any
                  employee option or similar incentive plan of the Company in
                  effect on the date hereof or agreed to by all Holders if put
                  into effect after the date hereof.

         (e)      ISSUANCE OF WARRANTS OR OTHER RIGHTS. If at any time or from
                  time to time the Company shall take a record of the holders of
                  its Common Units for the purpose of entitling them to receive
                  any distribution of, or shall otherwise issue, any warrants or
                  other rights to subscribe for, or purchase any additional
                  Common Units or any convertible securities convertible into
                  additional Common Units, and the consideration per unit for
                  which additional Common Units may at any time thereafter be
                  issuable pursuant to all such warrants and other rights or
                  pursuant to the terms of such convertible securities, as the
                  case may be, is less per unit than the Fair Market Value Per
                  Unit in effect immediately prior to issuance of such
                  additional Common Units, then the number of Warrant Units
                  issuable upon exercise of a Warrant shall be adjusted as
                  provided in SECTION 3(d), on the basis that (i) the maximum
                  number of additional Common Units issuable pursuant to all
                  such warrants or other rights or upon conversion of all such
                  convertible securities shall be deemed to have been issued as
                  of the date for determination of the Fair Market Value Per
                  Unit as hereinbelow provided, and (ii) the aggregate
                  consideration for such maximum number of additional Common
                  Units shall be deemed to be the minimum receivable pursuant to
                  such warrants or rights, or upon conversion of such
                  convertible securities, as
<PAGE>

                  the case may be. The date as of which Fair Marker Value Per
                  Unit shall be determined for purposes of this SECTION 3(e)
                  shall be the earliest of the date on which the Company shall
                  take a record of the holders of its Common Units, the date on
                  which the Company enters into a firm contract for the issuance
                  of such warrants, rights or convertible securities, and the
                  date of actual issuance thereof.

         (f)      SUPERSEDING ADJUSTMENTS. If, at any time after an adjustment
                  of the number of Warrant Units issuable upon exercise of a
                  Warrant shall have been made pursuant to the foregoing SECTION
                  3(e) on the basis of issuance of warrants or other rights, or
                  of convertible securities, or after an adjustment of the
                  number of Warrant Units issuable upon exercise of a Warrant
                  shall have been made pursuant to this SECTION 3(f),

                                    (i) such warrants or rights, or the
                           conversion right in such convertible securities,
                           shall expire and a portion thereof shall not have
                           been exercised or converted, as the case may be,
                           and/or

                                    (ii) the consideration per unit for which
                           Common Units are issuable pursuant the such warrants
                           or rights, or upon conversion of such convertible
                           securities, shall be increased solely by virtue of
                           provisions therein for an automatic increase in such
                           consideration upon the arrival of a specified date or
                           the occurrence of a specified event,

                  such previous adjustment shall be rescinded and annulled, and
                  the additional Common Units deemed issued by virtue of the
                  computation made in connection with such adjustment shall no
                  longer be deemed to have been issued. Thereupon a
                  re-computation shall be made as to the effect of such
                  warrants, rights or convertible securities, on the basis of

                                    (iii) treating the number of additional
                           Common Units, if any, theretofore actually issued or
                           issuable pursuant to such exercise or conversion as
                           having been issued on the date or dates of exercise
                           or conversion for the consideration actually received
                           or receivable therefor, and

                                    (iv) treating any such warrants or rights or
                           any such convertible securities which then remain
                           outstanding as having been granted or issued
                           immediately after the time of such increase of the
                           consideration per unit for which Common Units are
                           issuable under such warrants, rights or convertible
                           securities;

                  and, if and to the extent called for by the foregoing
                  provisions of this SECTION 3 on the basis aforesaid, a new
                  adjustment of the number of Warrant Units issuable upon
                  exercise of a Warrant shall be made, which new adjustment
                  shall supersede the previous adjustment so rescinded and
                  annulled.

         (g)      CONSIDERATION. For purposes of this SECTION 3, the
                  consideration per unit for any additional Common Units
                  issuable pursuant to any warrants or other rights shall
                  include the consideration for issuing such warrants or rights,
                  as well as the consideration payable upon exercise of the
                  same; and the consideration per unit for any additional Common
                  Units issuable upon conversion of any convertible securities
                  shall include the
<PAGE>

                  consideration for issuing such convertible securities
                  (including any consideration paid for issuance of warrants or
                  rights to subscribe for such convertible securities), as well
                  as the consideration payable upon exercise of the right of
                  conversion contained therein. The consideration paid or
                  payable in connection with any Common Units issued in an
                  underwritten public offering, or Rule 144A offering, shall be
                  determined without deducting underwriting discounts or
                  commissions.

                  SECTION 4.   COVENANTS.

         (a)      PRIVATE COMPANY INFORMATION. If, during the term of this
                  Agreement, the Company shall cease to be subject to the
                  periodic reporting obligations of Section 15(d) of the
                  Exchange Act, the Company will furnish, or will cause to be
                  furnished, to each Holder copies of the following financial
                  statements, reports and information:

                  (i)      promptly when available and in any event within 120
                           days after the close of each fiscal year, a
                           consolidated balance sheet at the close of such
                           fiscal year, and related consolidated statements of
                           operations and cash flows for such fiscal year, of
                           the Company and its subsidiaries (with comparable
                           information at the close of and for the prior fiscal
                           year), certified (in the case of consolidated
                           statements) without qualification by nationally
                           recognized independent public accountants; and

                  (ii)     promptly when available and in any event within 45
                           days after the close of each fiscal quarter,
                           consolidated balance sheets at the close of such
                           fiscal quarter, and consolidated statements of
                           operations and cash flows for such fiscal quarter and
                           for the period commencing at the close of the
                           previous fiscal year and ending with the close of
                           such fiscal quarter, of the Company and its
                           subsidiaries (with comparable information at the
                           close of and for the corresponding fiscal quarter of
                           the prior fiscal year and for the corresponding
                           portion of such prior fiscal year), certified by the
                           chief financial or executive officer of the General
                           Partner.

         (b)      PUBLIC COMPANY INFORMATION. So long as the Company is subject
                  to the periodic reporting requirements of Section 15(d) of the
                  Exchange Act, the Company will:

<PAGE>

                  (i)      file with the SEC on or before the required date all
                           regular or periodic reports required pursuant to the
                           Exchange Act and deliver to each Holder, promptly
                           upon its becoming available, one copy of each report,
                           notice or proxy statement sent by the Company to its
                           Limited Partners generally, and of each regular or
                           periodic report filed pursuant to the Exchange Act
                           and any registration statement or prospectus pursuant
                           to the Securities Act filed by the Company with (A)
                           the SEC or (B) any national securities exchange; and

                  (ii)     use its reasonable commercial efforts to make
                           publicly available information concerning the Company
                           sufficient to allow a Holder to dispose in accordance
                           with this Agreement of all or a portion of the
                           Warrant Units pursuant to Rule 144 (or any successor
                           provision).

         (c)      GOVERNMENTAL APPROVALS. The Company will use its reasonable
                  commercial efforts, and will cooperate with the Holders to,
                  secure all necessary consents, approvals, authorizations and
                  exemptions from all Governmental Authorities in connection
                  with the transactions contemplated hereby and the exercise of
                  the Warrants and the issuance of Common Units upon exercise of
                  the Warrants.

         (d)      TERMINATION OF RIGHTS UPON SALE TO THE PUBLIC. Notwithstanding
                  anything to the contrary set forth herein, the obligations of
                  the Company set forth in this SECTION 4 shall terminate with
                  respect to any Holder (including an underwriter) acquiring any
                  Warrants or Warrant Units pursuant to a registration statement
                  declared effective by the SEC under the Securities Act or in a
                  sale effected pursuant to Rule 144.

                  SECTION 5.   RESTRICTIONS ON TRANSFERS.

         (a)      TRANSFERS OF WARRANTS. A Holder may not dispose of or transfer
                  any Warrants now or hereafter owned, whether by sale,
                  assignment, gift, pledge, encumbrance or otherwise, except
                  pursuant to an available exemption from registration under
                  Federal and state securities laws PROVIDED, that this Section
                  shall not apply to a surrender of Warrant Certificates to the
                  Company in connection with the Warrants evidenced thereby.

         (b)      RESTRICTED SECURITIES. Warrants are transferable only in
                  accordance with SECTION 5(a).

         (c)      TRANSFERS OF WARRANT UNITS. A Holder may not dispose of or
                  transfer any Warrant Units now or hereafter owned, whether by
                  sale, assignment, gift, pledge, encumbrance or otherwise,
                  except pursuant to a registered sale under Federal securities
                  laws or pursuant to an available exemption from registration
                  under Federal and state securities laws.

                  SECTION 6. TERMINATION. This Agreement shall terminate and all
outstanding Warrants shall be canceled on the first to occur of (a) the fifth
anniversary of the Closing Date (the "TERMINATION DATE") and (b) the exercise or
cancellation of all Warrants issued pursuant to this Agreement.

                  SECTION 7.   REGISTRATION OF TRANSFERS AND EXCHANGES.
<PAGE>

         (a)      The Company shall from time to time register the initial
                  issuance and any transfer of any outstanding Warrant
                  Certificates made in accordance with SECTION 5 hereof in a
                  Warrant register to be maintained by the Company upon
                  surrender of such Warrant Certificates accompanied by a
                  written instrument or instruments of transfer in form
                  reasonably satisfactory to the Company, duly executed by the
                  Holder or Holders thereof or by the duly appointed legal
                  representative thereof or by a duly authorized attorney;
                  PROVIDED, HOWEVER, that prior to effecting such transfer, the
                  transferee shall agree (in a form reasonably satisfactory to
                  the Company) to be bound by the terms of this Agreement. Upon
                  any such registration of transfer, a new Warrant Certificate
                  shall be issued to the transferee(s) and the surrendered
                  Warrant Certificate shall be canceled. Until the Warrant
                  Certificate is transferred on the Warrant register of the
                  Company, the Company may treat the Holder as shown in the
                  Warrant register as the absolute owner of the Warrant
                  Certificate for all purposes, and notwithstanding any notice
                  to the contrary. The Company agrees that it will make the
                  Warrant register available for inspection by the Holders
                  during normal business hours at its office.

         (b)      By acceptance thereof, the Holders agree that, unless and
                  until the Company shall receive an opinion of counsel,
                  reasonably satisfactory to it in form, scope and substance
                  that such is not necessary to ensure compliance with the
                  securities laws, each Warrant Certificate and, subject to
                  SECTION 23 hereof, each certificate representing Warrant
                  Units, will bear the following legend (the "SECURITIES
                  LEGEND"):

                           "THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE
                           NOT BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933,
                           AS AMENDED, OR ANY STATE SECURITIES LAWS. SAID
                           SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE
                           ABSENCE OF SUCH REGISTRATION OR AN EXEMPTION FROM THE
                           REGISTRATION PROVISIONS OF SAID ACT OR LAWS. THE
                           SECURITIES REPRESENTED BY THIS CERTIFICATE ARE
                           SUBJECT TO THE TERMS OF A WARRANT AGREEMENT, DATED AS
                           OF JUNE 30, 2000, BETWEEN CORNERSTONE PROPANE
                           PARTNERS, L.P. (THE "COMPANY") AND NORTHWESTERN
                           CORPORATION, A COPY OF WHICH IS ON FILE AT THE MAIN
                           OFFICE OF THE COMPANY. ANY SALE OR TRANSFER OF THE
                           SECURITIES EVIDENCED BY THIS CERTIFICATE IS SUBJECT
                           TO THE TERMS OF THAT AGREEMENT AND ANY SALE OR
                           TRANSFER OF SUCH SECURITIES IN VIOLATION OF SAID
                           AGREEMENT SHALL BE INVALID."

         (c)      Warrant Certificates may be exchanged at the option of the
                  Holder(s) thereof when surrendered to the Company at its
                  office for another Warrant Certificate or other Warrant
                  Certificates of like tenor and representing in the aggregate a
                  like number of Warrants, including, without limitation, upon
                  an adjustment in the Exercise Price or in the number of
                  Warrant Units purchasable upon exercise of the Warrants.
                  Warrant Certificates surrendered for exchange shall be
                  canceled.
<PAGE>

                  SECTION 8. PAYMENT OF TAXES. The Company will pay all stamp,
transfer and similar taxes in connection with the issuance, sale and delivery of
the Warrants hereunder, as well as all such taxes attributable to the initial
issuance of Warrant Units upon the exercise of Warrants and payment of the
appropriate Exercise Price. The Company will not, however, be required to pay
any such taxes imposed in connection with any transfer of any Warrants or
Warrant Units or any Federal or state income taxes payable in respect of any
Holder's purchase, ownership, sale, transfer, exercise or other disposition of
Warrants or Warrant Units.

                  SECTION 9. MUTILATED OR MISSING WARRANT CERTIFICATES. Upon
receipt by the Company of evidence reasonably satisfactory to the Company (which
shall include an affidavit of the Holder) that any Warrant Certificate shall
have been mutilated, lost, stolen or destroyed and, in the case of loss, theft
or destruction, a customary indemnity agreement from the Holder of such Warrant
Certificate and (if such Holder is other than NOR or an affiliate of NOR) a lost
certificate indemnity bond from a reputable bonding or insurance company in an
amount acceptable to the Company, the Company shall issue, in exchange and
substitution for and upon cancellation of the mutilated Warrant Certificate, or
in lieu of and substitution for the Warrant Certificate lost, stolen or
destroyed, a new Warrant Certificate of like tenor and representing an
equivalent number of Warrants.

                  SECTION 10. RESERVATION OF WARRANT UNITS. The Company will at
all times that any Warrant is exercisable reserve and keep available, free from
preemptive or similar rights, out of the aggregate of its authorized but
unissued Common Units, for the purpose of enabling it to satisfy any obligation
to issue Warrant Units upon exercise of Warrants, the maximum number of units of
each class of partnership interest constituting a part of the Warrant Units
which may then be deliverable upon the exercise of all outstanding Warrants. The
Company or, if appointed, the transfer agent for units of each class of
partnership interest of the Company (the "TRANSFER AGENT") and every subsequent
transfer agent for any units of the Company's partnership interest issuable upon
the exercise of the Warrants will be irrevocably authorized and directed at all
times to reserve such number of authorized units as shall be required for such
purpose. The Company will keep a copy of this Agreement on file with the
Transfer Agent and with every subsequent transfer agent for any units of the
Company's partnership interests issuable upon the exercise of the rights of
purchase represented by the Warrants. The Company will furnish such Transfer
Agent a copy of all notices of adjustments, and certificates related thereto,
transmitted to Holders pursuant to SECTION 12. Before taking any action which
would cause an adjustment pursuant to SECTION 3 to the maximum number of Warrant
Units deliverable upon the exercise of all outstanding Warrants pursuant to
SECTION 2(a), the Company shall cause to be authorized additional Common Units
such that the sum of such maximum number of Common Units deliverable upon
exercise of all outstanding Warrants and the number of Common Units outstanding
as of such date does not exceed the number of Common Units authorized pursuant
to the Company's Partnership Agreement.

                  SECTION 11. FRACTIONAL INTERESTS. The Company shall not be
required to issue fractional Warrant Units on the exercise of Warrants. If more
than one Warrant shall be presented for exercise in full at the same time by the
same Holder, the number of Warrant Units which shall be issuable upon exercise
thereof shall be computed on the basis of the aggregate number of Warrant Units
purchasable on exercise of the Warrants so presented. If any fraction of a
Warrant Unit would, except for the provisions of this SECTION 11, be issuable on
the exercise of any Warrants (or specified portion thereof), the Company shall
pay an amount in cash equal to the Fair Market Value Per Unit calculated as of
the day immediately preceding the date the Warrant is presented for exercise,
multiplied by such fraction.

                  SECTION 12. NOTICE TO WARRANT HOLDERS. Upon any adjustment of
the Exercise Price or number or type of securities purchasable upon exercise of
the Warrants pursuant to SECTION 3, the Company shall promptly thereafter (i)
cause to be filed with the Company a
<PAGE>

certificate of the chief financial officer of the General Partner of Company
setting forth the Exercise Price and the number and type of securities or other
property constituting Warrant Units after such adjustment and setting forth in
reasonable detail the method of calculation and the facts upon which such
calculations are based and, in the case of an adjustment pursuant to SECTION
3(b), setting forth the number and type of securities or other property
constituting Warrant Units (or portion thereof) issuable, after such adjustment
in the Exercise Price or number of Warrant Units, upon exercise of the Warrants,
upon exercise of a Warrant and payment of the adjusted Exercise Price, and (ii)
cause to be given to each of the Holders of the Warrant Certificates written
notice of such adjustments, together with a copy of such certificate. Where
appropriate, such notice may be given in advance and included as a part of the
notice required to be given under the other provisions of this SECTION 12. In
the event:

         (a)      the Company shall authorize the payment of any distribution to
                  holders of Common Units of the Company; or

         (b)      of any capital reorganization, reclassification,
                  recapitalization, consolidation, merger, or unit exchange or
                  sale, lease, transfer, conveyance or other disposition to
                  which the adjustment provisions of SECTION 3(b) apply, or a
                  purchase, tender or exchange offer for Common Units or other
                  securities constituting part of the Warrant Units (whether by
                  the Company or some other party); or

         (c)      of the voluntary or involuntary dissolution, liquidation or
                  winding up of the Company; or

         (d)      the Company proposes to take any action that would require an
                  adjustment of the Exercise Price or number of Warrant Units
                  for which the Warrants are exercisable;

then the Company shall cause to be given to each of the Holders, at least 20
days prior to the applicable record date hereinafter specified (or promptly in
the case of events for which there is no record date), a written notice stating
(as applicable) (i) the date as of which the holders of record of Common Units
entitled to receive any such dividends or distribution are to be determined,
(ii) the date on which any such reclassification, recapitalization or
reorganization, consolidation, merger, unit exchange, sale, lease, transfer,
conveyance or disposition to which the adjustment provisions of SECTION 3(b)
apply or any such dissolution, liquidation or winding up is expected to become
effective or be consummated, or (iii) the initial expiration date set forth in
any purchase, tender or exchange offer for partnership interests, and the date
as of which it is expected that holders of record of partnership interests or
other securities constituting a part of the Warrant Units (or securities into
which the Warrant Units may be converted) shall be entitled to exchange such
shares or securities for securities or other property, if any, deliverable upon
such reclassification, recapitalization, reorganization, consolidation, merger,
amalgamation, share exchange, sale, lease, conveyance, transfer, disposition,
dissolution, liquidation or winding up.

                  SECTION 13. NOTICES. All notices, consents, approvals,
agreements and other communications provided hereunder shall be in writing and
delivered personally, by mail, by overnight courier (providing proof of
delivery) or by telecopy and shall be sufficiently given to NOR and the Company
if addressed or delivered to them at the following addresses:
<PAGE>

                  If to Company:        Cornerstone Propane Partners, L.P.
                                        432 Westridge Drive
                                        Watsonville, CA   95076

                                        Attention: Chief Financial Officer
                                        Telephone No.: (831) 724-1921
                                        Facsimile No.: (831) 724-4038

                  If to NOR:            Northwestern Corporation
                                        125 S. Dakota Avenue, Suite 1100
                                        Sioux Falls, SD 57104-6403
                                        Attention:  General Counsel
                                        Telephone No.: (605) 978-2917
                                        Facsimile No.:  (605) 978-2810

or if to any other Holder at such address for such Holder as may appear in the
Warrant register, or at such other address as any party may designate to any
other party by written notice. All such notices and communications shall be
deemed to have been duly given: (i) at the time delivered by hand, if personally
delivered, (ii) when received, if deposited in the mail, postage prepaid, (iii)
when transmission is verified, if telecopied, and (iv) on the next Business Day,
if timely delivered to an air courier guaranteeing overnight delivery.

                  SECTION 14. SUCCESSORS. Except as otherwise expressly provided
herein or in the Warrants, all covenants and agreements of this Agreement by or
on behalf of any of the parties hereto shall bind and inure to the benefit of
the respective successors and assigns, including those by operation of law,
merger or consolidation. In addition, except as otherwise expressly provided in
the Warrants, and whether or not any express assignment has been made, the
provisions of this Agreement which are for NOR's benefit as a purchaser or
Holder of a Warrant or Warrant Units are also for the benefit of, and
enforceable by, any subsequent Holder of such a Warrant or Warrant Units.

                  SECTION 15. GOVERNING LAW. This Agreement, the Warrants and
the Warrant Units shall be governed by those provisions of the Delaware Revised
Uniform Limited Partnership Act, 6 Del. Section 17-101 et. seq., and Article 8
of the Delaware Uniform Commercial Code, which are necessarily applicable to
securities issued by a Delaware limited partnership and otherwise shall be
deemed to be a contract made under the laws of the State of New York and for all
purposes shall be construed in accordance with the internal laws of said state.

                  SECTION 16. BENEFITS OF THIS AGREEMENT. Except as otherwise
provided in SECTION 14 hereof, nothing in this Agreement shall be construed to
give to any Person other than the Company and the Holders any legal or equitable
right, remedy or claim under this Agreement; this Agreement shall be for the
sole and exclusive benefit of the Company and the Holders.

                  SECTION 17. COUNTERPARTS. This Agreement may be executed in
any number of counterparts and each such counterpart shall for all purposes be
deemed to be an original, and all such counterparts shall together constitute
one and the same instrument.

                  SECTION 18. AMENDMENT; WAIVERS. Except as otherwise expressly
provided herein, the provisions of this Agreement may be amended or waived and
the Company may take any action herein prohibited, or fail to take any action
herein required to be performed by it if, but only if, the Company has obtained
the written consent of the Holders of (x) Warrant Certificates
<PAGE>

evidencing the right to purchase a majority of the sum of all Warrant Units not
yet issued and outstanding for which Warrants are currently exercisable, plus
(y) all outstanding Warrant Units (other than any such sold in a registered
public offering under the Securities Act). No failure or delay by any party in
exercising any right or remedy hereunder shall operate as a waiver thereof, nor
shall a waiver of a particular right or remedy on one occasion be deemed a
waiver of any other right or remedy or a waiver of the same right or remedy on
any subsequent occasion.

                  SECTION 19. JURISDICTION. Each of the parties hereto hereby
agrees that any legal action or proceeding against such party with respect to
this Agreement, the Warrants or the Warrant Units may be brought in the courts
of the State of New York in the Borough of Manhattan, City and State of New
York, or of the United States of America for the Southern District of New York
as the other party may elect, and, by execution and delivery hereof, such party
accepts and consents for itself and in respect of its property, generally and
unconditionally, the jurisdiction of the aforesaid courts and agrees that such
jurisdiction shall be exclusive, unless waived by the other party in writing,
with respect to any action or proceeding brought by such party against the other
party. Each of the parties hereto irrevocably consents to the service of process
out of any of the aforementioned courts in any such action or proceeding by the
mailing of the copies thereof by certified mail, return receipt requested,
postage prepaid, to it at its address set forth herein, such service to become
effective upon the earlier of (i) the date ten calendar days after such mailing
and (ii) any earlier date permitted by applicable law.

                  SECTION 20. SPECIFIC PERFORMANCE. The Company and the Holders
recognize that the rights of the Holder(s) and the Company under this Agreement
are unique and, accordingly, the Holder(s) and the Company shall, in addition to
such other remedies as may be available to any of them at law or in equity, have
the right to enforce their rights hereunder and thereunder by actions for
injunctive relief and specific performance to the extent permitted by law. The
Company and the Holders agree that monetary damages would not be adequate
compensation for any loss incurred by reason of a breach by it of the provisions
of this Agreement and the Company and each of the Holders hereby agrees to waive
in any action for specific performance the defense that a remedy at law would be
adequate. This Agreement is not intended to limit or abridge any rights of the
Holder(s) or the Company which may exist apart from this Agreement.

                  SECTION 21. ENTIRE AGREEMENT. The parties hereto agree that
this Agreement constitutes the entire agreement among the parties with respect
to the subject matter hereof and supersedes all prior agreements and
understandings between them as to such subject matter; and there are no
restrictions, agreements, arrangements, oral or written, between any or all of
the parties relating to the subject matter hereof which are not fully expressed
or referred to herein or therein.

                  SECTION 22. SEVERABILITY. If any provision of this Agreement
shall be held or deemed to be, or shall in fact be, invalid, inoperative or
unenforceable as applied to any particular case in any jurisdiction or
jurisdictions, or in all jurisdictions or in all cases, because of the conflict
of any provision with any constitution, statute, rule or public policy, or for
any other reason, such circumstances shall not have the effect of rendering the
provision or provisions in question, invalid, inoperative or unenforceable in
any other jurisdiction or in any other case or circumstance or of rendering any
other provision or provisions herein contained invalid, inoperative or
unenforceable to the extent that such other provisions are not themselves
actually in conflict with such constitution, statute, rule or public policy, but
this Agreement shall be reformed and construed in any such jurisdiction or case
as if such invalid, inoperative or unenforceable provision had never been
contained herein and such provision reformed so that it would be valid,
operative and enforceable to the maximum extent permitted in such jurisdiction
or in such case.
<PAGE>

                  SECTION 23. REGISTRATION UNDER SECURITIES ACT OF 1933, AS
                              AMENDED.

         (a)      As used in this SECTION 23, the following terms shall have the
                  following meanings:

                  (i)      The terms "REGISTER," "REGISTERED" and "REGISTRATION"
                           refer to the registration effected by preparing and
                           filing a registration statement in compliance with
                           the Securities Act, and the declaration or ordering
                           of the effectiveness of such registration statement.

                  (ii)     "REGISTRABLE SECURITIES" shall mean the Common Units
                           issuable upon exercise of the Warrants (or in
                           substitution or exchange for any or all such Common
                           Units, or in subsequent substitutions or exchanges)
                           and the PIK Units, if any shall be outstanding;
                           PROVIDED, HOWEVER, that securities shall only be
                           treated as Registrable Securities if and only for so
                           long as they (A) have not been disposed of pursuant
                           to a registration statement declared effective by the
                           SEC, (B) have not been sold in a transaction exempt
                           from the registration and prospectus delivery
                           requirements of the Securities Act so that all
                           transfer restrictions and restrictive legends with
                           respect thereto are removed upon the consummation of
                           such sale, and (C) are held by a Holder (whether the
                           original Holder or a Holder that is a permitted
                           transferee pursuant to SECTION 23(j)).

                  (iii)    "REGISTRATION EXPENSES" shall mean all expenses
                           incurred by the Company in complying with SECTION
                           23(b) OR (c) hereof, including, without limitation,
                           all registration, qualification and filing fees,
                           printing expenses, escrow fees, fees and expenses of
                           counsel for the Company, blue sky fees and expenses
                           and the expense of any special audits incident to or
                           required by any such registration (including Selling
                           Expenses for each Holder).

                  (iv)     "REGISTRATION PERIOD" shall have the meaning ascribed
                           to such term in SECTION 23(d).

                  (v)      "SELLING EXPENSES" shall mean all reasonable fees,
                           and the expenses, of one firm of legal counsel for
                           all Holders whose Registrable Securities are to be
                           included in a registration.

         (b)      DEMAND REGISTRATION RIGHTS.

                  (i)      Subject to the provisions contained in this SECTION
                           23(b), any Holder or Holders may request (each, a
                           "REQUESTING HOLDER") on not more than two (2)
                           occasions in writing (a "DEMAND REQUEST") that the
                           Company effect the registration under the Securities
                           Act of that number of Common Units constituting
                           Registrable Securities requested and owned by the
                           Requesting Holder(s) (a "DEMAND REGISTRATION");
                           PROVIDED, HOWEVER, the Registrable Securities to be
                           included in such Demand Registration comprise at
                           least 100,000 Common Units (subject to adjustment as
                           herein provided); PROVIDED, FURTHER, that the Company
                           will in no event be required to effect more than one
                           Demand Registration for the Holders in total in any
                           12-month period. Upon receipt of a Demand Request,
                           the Company will cause to be included in a
                           registration statement on an appropriate form under
                           the Securities Act, filed with the SEC within 90
<PAGE>

                           days after receiving a Demand Request (the "REQUIRED
                           FILING DATE"), such Registrable Securities as may be
                           requested by Joining Holders joining in such request
                           pursuant to SECTION 23(b)(ii). The Company shall use
                           its reasonable best efforts to cause any such
                           registration statement to be declared effective by
                           the SEC as promptly as practicable after such filing
                           but in any event not later than 150 days (or such
                           longer period, not in excess of 240 days, during
                           which the Company shall be diligently pursuing having
                           such registration statement so declared effective)
                           following the date of the Demand Request.

                  (ii)     If at any time the Company proposes to register
                           Common Units for the account of the Requesting
                           Holders pursuant to SECTION 23(b)(i) then the Company
                           shall give written notice of such proposed filing to
                           the Holders of Warrant Certificates as soon as
                           practicable (but in no event less than 30 days before
                           the anticipated filing date). Upon the written
                           request of any such Holder, received by the Company
                           no later than the 10th business day after receipt by
                           such Holder of the notice sent by the Company (each
                           such Holder a "JOINING HOLDER"), to register, on the
                           same terms and conditions as the securities otherwise
                           being sold pursuant to such Demand Registration, any
                           of its Registrable Securities, the Company will use
                           its best efforts to cause the Registrable Securities
                           to be included in the securities to be covered by the
                           registration statement proposed to be filed by the
                           Company on the same terms and conditions as any
                           similar securities included therein, all to the
                           extent requisite to permit the sale or other
                           disposition by each Holder of the Registrable
                           Securities so registered.

                  (iii)    A registration will not count as a Demand
                           Registration until it has become effective; PROVIDED,
                           HOWEVER, that if, after it has become effective, an
                           offering of Registrable Securities pursuant to a
                           registration statement is terminated by any stop
                           order, injunction, or other order of the SEC or other
                           governmental agency or court, such registration
                           pursuant thereto will be deemed not to have been
                           effected and will not count as a Demand Registration.

                  (iv)     Unless the Requesting Holder otherwise elects, all
                           Demand Registrations will be underwritten offerings.
                           With respect to any offering of Registrable
                           Securities pursuant to a Demand Registration in the
                           form of an underwritten offering, the Company shall
                           select an investment banking firm or firms of
                           national standing to manage the underwritten
                           offering, subject to the consent of the Requesting
                           Holders of a majority of the Registrable Securities
                           for such registration, which consent shall not be
                           withheld unreasonably.

                  (v)      Securities to be sold for the account of any Person
                           or entity (including the Company) other than
                           Requesting Holders or Joining Holders may be included
                           in a Demand Registration unless the managing
                           underwriter or underwriters shall advise the
                           Requesting Holders in writing that the inclusion of
                           such securities will materially and adversely affect
                           the price or success of the offering (a "MATERIAL
                           ADVERSE EFFECT"). Furthermore, in the event that the
                           managing underwriter or underwriters shall advise the
                           Requesting Holders that even after exclusion of all
                           securities of the other Persons or entities pursuant
                           to the immediately preceding sentence, the amount of
                           Registrable Securities proposed to be included in
                           such

<PAGE>

                           Demand Registration by Requesting Holders and
                           Joining Holders is sufficiently large to cause a
                           Material Adverse Effect, the number of Common Units
                           to be included in such Demand Registration shall be
                           allocated among all Holders pro rata based on the
                           ratio the number of Common Units each such Holder
                           requests be included bears to the total number of
                           Common Units of all Holders that have been requested
                           be included in such registration.

         (c)      PIGGY-BACK REGISTRATION RIGHTS. (i) The Company agrees that
                  if, at any time, and from time to time, commencing on the date
                  that is six (6) months from the Closing Date and ending on the
                  date that is five (5) years from the Closing Date, the General
                  Partner of the Company shall authorize the filing of a
                  registration statement under the Securities Act (other than a
                  registration statement on Form S-8, Form S-4 or any other form
                  or successor form that does not include substantially the same
                  information as would be required in a form for the general
                  registration of securities) in connection with the proposed
                  offer of any of its securities by it or any of its
                  unitholders, the Company shall, (A) promptly notify the
                  Holders in writing that such registration statement will be
                  filed and that Registrable Securities will be included in such
                  registration statement at any Holder's request, (B) cause such
                  registration statement to cover all such Registrable
                  Securities for which the Holder thereof requests inclusion,
                  (C) use its reasonable best efforts to cause such registration
                  statement to become effective as soon as practicable and (D)
                  take all other action necessary under any Federal or state law
                  or regulation of any governmental authority to permit all such
                  Registrable Securities to be sold or otherwise disposed of,
                  and will maintain such compliance with each such Federal and
                  state law and regulation of any governmental authority for the
                  period necessary for the Holders to effect the proposed sale
                  or other disposition, but in no event greater than six (6)
                  months.

                  (ii)     Notwithstanding any other provision in this Warrant
                           Agreement, the Company may at any time abandon or
                           delay any registration commenced by the Company. In
                           the event of such an abandonment by the Company, the
                           Company shall not be required to continue
                           registration of the Registrable Securities requested
                           by the Holder for inclusion and the Holder shall
                           retain the right to request inclusion of the
                           Registrable Securities in accordance with SECTION
                           23(c)(i).

                  (iii)    Securities to be sold for the account of any Person
                           or entity (other than the Company) requesting
                           inclusion thereof in a registration pursuant to this
                           SECTION 23(c) shall be included in such registration
                           unless the managing underwriter or underwriters shall
                           advise the Company and the Holders requesting such
                           inclusion in writing that the inclusion of all such
                           securities will materially and adversely affect the
                           price or success of the offering. In the event that
                           the managing underwriter or underwriters shall so
                           advise the Company and the requesting Holders, the
                           number of Common Units to be included in such
                           registration shall be allocated (a) as between the
                           Company and such Holders based on the ratio the
                           number of Common Units the Company and each such
                           Holder respectively propose be included bears to the
                           total number of Common Units the Company and all such
                           Holders have proposed be included, and (b) among all
                           Holders pro rata based on the ratio the number of
                           Common Units each such Holder requests be included
                           bears to the total number of Common Units of all
                           Holders that have been requested be included in such
                           registration.
<PAGE>

         (d)      OBLIGATIONS. Whenever required under this Warrant to include
                  Registrable Securities in a Company registration statement,
                  the Company shall, as expeditiously as is reasonably possible:

                  (i)      use its reasonable best efforts to keep such
                           registration, and any qualification, exemption or
                           compliance under state securities laws which the
                           Company determines to obtain, continuously effective
                           until the Holders have completed the distribution
                           described in the registration statement relating
                           thereto or six (6) months, whichever is shorter. The
                           period of time during which the Company is required
                           hereunder to keep the Registration Statement
                           effective being referred to herein as the
                           "REGISTRATION PERIOD"; and

                  (ii)     advise the Holders:

                           (A) when such registration statement or any amendment
                  thereto has been filed with the SEC and when such registration
                  statement or any post-effective amendment thereto has become
                  effective;

                           (B) of any request by the SEC for amendments or
                  supplements to such registration statement or the prospectus
                  included therein or for additional information;

                           (C) of the issuance by the SEC of any stop order
                  suspending the effectiveness of such registration statement or
                  the initiation of any proceedings for such purpose;

                           (D) of the receipt by the Company of any notification
                  with respect to the suspension of the qualification of the
                  Registrable Securities included therein for sale in any
                  jurisdiction or the initiation or threatening of any
                  proceeding for such purpose; and

                           (E) of the happening of any event that requires the
                  making of any changes in such registration statement or the
                  prospectus so that, as of such date, the statements therein
                  are not misleading and do not omit to state a material fact
                  required to be stated therein or necessary to make the
                  statements therein (in the case of the prospectus, in the
                  light of the circumstances under which they were made) not
                  misleading;

                  (iii)    make every reasonable effort to obtain the withdrawal
                           of any order suspending the effectiveness of any
                           Registration Statement at the earliest possible time;

                  (iv)     furnish to each Holder, without charge, at least one
                           copy of such registration statement and any
                           post-effective amendment thereto, including financial
                           statements and schedules, and, if the Holder so
                           requests in writing, all exhibits (including those
                           incorporated by reference) in the form filed with the
                           SEC;

                  (v)      during the Registration Period, deliver to each
                           Holder, without charge, as many copies of the
                           prospectus included in such registration statement
                           and any amendment or supplement thereto as such
                           Holder may reasonably request; and the Company
                           consents to the use, consistent with
<PAGE>

                           the provisions hereof, of the prospectus or any
                           amendment or supplement thereto by each of the
                           selling Holders of Registrable Securities in
                           connection with the offering and sale of the
                           Registrable Securities covered by the prospectus or
                           any amendment or supplement thereto. In addition,
                           upon the reasonable request of the Holder and subject
                           in all cases to confidentiality protections
                           reasonably acceptable to the Company, the Company
                           will meet with the Holder or Holders of more than 50%
                           of the Warrant Units included in such registration at
                           the Company's headquarters to discuss all information
                           relevant for disclosure in such registration
                           statement covering the Registrable Securities, and
                           will otherwise cooperate with any Holder conducting
                           an investigation for the purpose of reducing or
                           eliminating such Holder's exposure to liability under
                           the Securities Act, including the reasonable
                           production of information at the Company's
                           headquarters;

                  (vi)     during the Registration Period, deliver to each
                           Holder, without charge, (A) as soon as practicable
                           (but in the case of the annual report of the Company
                           to its unitholders, within 120 days after the end of
                           each fiscal year of the Company) one copy of: (1) its
                           annual report to its unitholders, if any (which
                           annual report shall contain financial statements
                           audited in accordance with generally accepted
                           accounting principles in the United States of America
                           by a firm of certified public accountants of
                           recognized standing); (2) if not included in
                           substance in its annual report to unitholders, its
                           annual report on Form 10-K (or similar form); (3)
                           each of its quarterly reports to its unitholders,
                           and, if not included in substance in its quarterly
                           reports to unitholders, its quarterly report on Form
                           10-Q (or similar form), and (4) a copy of the full
                           Registration Statement (the foregoing, in each case,
                           excluding exhibits); and (B) upon reasonable request,
                           all exhibits excluded by the parenthetical to the
                           immediately preceding clause (4), and all other
                           information prepared by the Company that is generally
                           available to the public;

                  (vii)    prior to any public offering of Registrable
                           Securities pursuant to any Registration Statement,
                           register or qualify or obtain an exemption for offer
                           and sale under the securities or blue sky laws of
                           such United States jurisdictions as any of the
                           Holders whose Registrable Securities are included in
                           such registration reasonably requests in writing,
                           PROVIDED that the Company shall not for any such
                           purpose be required to qualify generally to transact
                           business as a foreign corporation in any jurisdiction
                           where it is not so qualified or to consent to general
                           service of process in any such jurisdiction, and do
                           any and all other acts or things reasonably necessary
                           or advisable to enable the offer and sale in such
                           jurisdictions of the Registrable Securities covered
                           by such registration statement;

                  (viii)   cooperate with the Holders to facilitate the timely
                           preparation and delivery of certificates representing
                           Registrable Securities to be sold pursuant to any
                           Registration Statement free of any restrictive
                           legends to the extent not required at such time and
                           in such denominations and registered in such names as
                           Holders may request at least three (3) business days
                           prior to sales of Registrable Securities pursuant to
                           such registration statement;

                  (ix)     upon the occurrence of any event contemplated by
                           SECTION 23(d)(ii)(E) above, the Company shall
                           promptly prepare a post-effective amendment
<PAGE>

                           to such registration statement or a supplement to the
                           related prospectus, or file any other required
                           document so that, as thereafter delivered to
                           purchasers of the Registrable Securities included
                           therein, the prospectus will not include any untrue
                           statement of a material fact or omit to state any
                           material fact necessary to make the statements
                           therein, in the light of the circumstances under
                           which they were made, not misleading; and

                  (x)      use its reasonable best efforts to comply with all
                           applicable rules and regulations of the SEC, and will
                           make generally available to the Holders not later
                           than 45 days (or 90 days if the fiscal quarter is the
                           fourth fiscal quarter) after the end of its fiscal
                           quarter in which the first anniversary date of the
                           effective date of such registration statement occurs,
                           an earnings statement satisfying the provisions of
                           Section 11(a) of the Securities Act.

         (e)      FURNISH INFORMATION. It shall be a condition precedent to the
                  obligation of the Company to take any action pursuant to this
                  Warrant Agreement with respect to the Registrable Securities
                  of any selling Holder that such Holder shall furnish to the
                  Company such information regarding the Holder, the Registrable
                  Securities held by the Holder, and the intended method of
                  disposition of such securities as shall be reasonably required
                  by the Company to effect the registration of such Holder's
                  Registrable Securities.

         (f)      EXPENSES OF COMPANY REGISTRATION. The Company shall bear and
                  pay all Registration Expenses incurred in connection with any
                  registration, filing or qualification of Registrable
                  Securities with respect to the registration pursuant to
                  SECTION 23(b) OR (c) for each Holder relating or apportionable
                  thereto. Notwithstanding the foregoing, each Holder shall pay
                  all Registration Expenses that such Holder is required to pay
                  under applicable law.

         (g)      UNDERWRITING REQUIREMENTS. In connection with any offering
                  involving an underwriting of the Company's partnership
                  interests, the Company shall not be required under SECTION
                  23(c) to include any Holder's Registrable Securities in such
                  underwriting unless such Holder accepts the terms of the
                  underwriting as agreed upon between the Company and the
                  underwriters selected by it (or by other Persons entitled to
                  select the underwriters), and then only in such quantity as
                  the underwriters determine in their reasonable discretion will
                  not jeopardize the success of the offering by the Company. If
                  the total number of securities, including Registrable
                  Securities, requested by unitholders to be included in such
                  offering exceeds the number of securities sold other than by
                  the Company that the underwriters determine in their
                  reasonable discretion is compatible with the success of the
                  offering, then the Company shall be required to include in the
                  offering only that number of such securities, including
                  Registrable Securities, which the underwriters determine in
                  their reasonable discretion will not jeopardize the success of
                  the offering (the securities so included to be apportioned pro
                  rata among the selling unitholders having registration rights
                  according to the total number of securities entitled to be
                  included therein owned by such selling unitholders, or in such
                  other proportions as mutually agreed to by such selling
                  unitholders). For purposes of the preceding parenthetical
                  expression concerning apportionment, for any selling
                  unitholder who is a holder of Registrable Securities and is a
                  partnership or corporation, the partners, retired partners and
                  stockholders of such holder, or the estates and family members
                  of any such partners and retired partners and any trusts for
                  the benefit of any of the foregoing Persons shall be deemed to
                  be a single "selling unitholder", and any
<PAGE>

                  pro-rata reduction with respect to such "selling unitholder"
                  shall be based upon the aggregate number of units carrying
                  registration rights owned by all entities and individuals
                  included in such "selling unitholder", as defined in this
                  sentence. The number of Registrable Securities to be included
                  in a registration pursuant to this Agreement shall not be
                  limited by units sought to be included by unitholders with no
                  registration rights.

         (h)      DELAY OF REGISTRATION. No Holder shall have any right to
                  obtain or seek an injunction restraining or otherwise delaying
                  any such registration as the result of any controversy that
                  might arise with respect to the interpretation or
                  implementation of this Warrant Agreement.

         (i)      INDEMNIFICATION. In the event that any Registrable Securities
                  are included in a registration statement under this Warrant
                  Agreement:

                  (i)      To the extent permitted by law, the Company will
                           indemnify and hold harmless each Holder, any
                           underwriter (as defined in the Securities Act) for
                           such Holder and each Person, if any, who controls
                           such Holder or underwriter within the meaning of the
                           Securities Act or the Exchange Act, against any
                           losses, claims, damages, or liabilities (joint or
                           several) to which they may become subject under the
                           Securities Act, or the Exchange Act, insofar as such
                           losses, claims, damages, or liabilities (or actions
                           in respect thereof) arise out of or are based upon
                           any of the following statements, omissions or
                           violations (collectively a "VIOLATION"): (A) any
                           untrue statement or alleged untrue statement of a
                           material fact contained in such registration
                           statement, including any preliminary prospectus or
                           final prospectus contained therein or any amendments
                           or supplements thereto or (B) the omission or alleged
                           omission to state therein a material fact required to
                           be stated therein, or necessary to make the
                           statements therein not misleading, and the Company
                           will pay to each such Holder, underwriter or
                           controlling Person, as incurred, any legal or other
                           expenses reasonably incurred by them in connection
                           with investigating or defending any such loss, claim,
                           damage, liability, or action; PROVIDED, HOWEVER, that
                           the indemnity agreement contained in this SECTION
                           23(i)(i) shall not apply to amounts paid in
                           settlement of any such loss, claim, damage,
                           liability, or action if such settlement is effected
                           without the consent of the Company (which consent
                           shall not be unreasonably withheld), nor shall the
                           Company be liable in any such case for any such loss,
                           claim, damage, liability, or action to the extent
                           that it arises out of or is based upon a violation
                           which occurs in reliance upon and in conformity with
                           written information furnished expressly for use in
                           connection with such registration by any such Holder,
                           underwriter or controlling Person.

                  (ii)     To the extent permitted by law, each selling Holder
                           will indemnify and hold harmless the Company and the
                           General Partner, each of their directors, each of
                           their officers who has signed the registration
                           statement, each Person, if any, who controls the
                           Company within the meaning of the Securities Act, any
                           underwriter, any other Holder selling securities in
                           such registration statement and any controlling
                           Person of any such underwriter or other Holder,
                           against any losses, claims, damages, or liabilities
                           (joint or several) to which any of the foregoing
                           Persons may become subject, under the Securities Act,
                           or the Exchange Act, insofar as such losses, claims,
                           damages, or liabilities (or actions in respect
                           thereto)
<PAGE>

                           arise out of or are based upon any Violation, in each
                           case to the extent (and only to the extent) that such
                           Violation occurs in reliance upon and in conformity
                           with written information furnished by such Holder
                           expressly for use in connection with such
                           registration; and each such Holder will pay, as
                           incurred, any legal or other expenses reasonably
                           incurred by any Person intended to be indemnified
                           pursuant to this SECTION 23(i)(ii), in connection
                           with investigating or defending any such loss, claim,
                           damage, liability, or action; PROVIDED, HOWEVER, that
                           the indemnity agreement contained in this SECTION
                           23(i)(ii) shall not apply to amounts paid in
                           settlement of any such loss, claim, damage, liability
                           or action if such settlement is effected without the
                           consent of the Holder, which consent shall not be
                           unreasonably withheld; PROVIDED, that, in no event
                           shall any indemnity under this SECTION 23(i)(ii)
                           exceed the net proceeds (after deducting the
                           underwriters' discount but before deducting other
                           expenses) from the offering received by such Holder.

                  (iii)    Promptly after receipt by an indemnified party under
                           this SECTION 23 of notice of the commencement of any
                           action (including any governmental action), such
                           indemnified party shall, if a claim in respect
                           thereof is to be made against any indemnifying party
                           under this SECTION 23, deliver to the indemnifying
                           party a written notice of the commencement thereof
                           and the indemnifying party shall have the right to
                           participate in, and, to the extent the indemnifying
                           party so desires, jointly with any other indemnifying
                           party similarly notified, to assume the defense
                           thereof with counsel selected by the indemnifying
                           party and approved by the indemnified party (whose
                           approval shall not be unreasonably withheld);
                           PROVIDED, HOWEVER, that an indemnified party
                           (together with all other indemnified parties which
                           may be represented without conflict by one counsel)
                           shall have the right to retain one separate counsel,
                           with the fees and expenses to be paid by the
                           indemnifying party, if representation of such
                           indemnified party by the counsel retained by the
                           indemnifying party would be inappropriate due to
                           actual or potential differing interests between such
                           indemnified party and any other party represented by
                           such counsel in such proceeding. The failure to
                           deliver written notice to the indemnifying party
                           within a reasonable time of the commencement of any
                           such action, if prejudicial to its ability to defend
                           such action, shall relieve such indemnifying party of
                           any liability to the indemnified party under this
                           SECTION 23, but the omission so to deliver written
                           notice to the indemnifying party will not relieve it
                           of any liability that it may have to any indemnified
                           party otherwise than under this SECTION 23.

                  (iv)     To the extent permitted by law, if the
                           indemnification provided for in this SECTION 23 is
                           held by a court of competent jurisdiction to be
                           unavailable to an indemnified party with respect to
                           any loss, liability, claim, damage, or expense
                           referred to therein, then the indemnifying party, in
                           lieu of indemnifying such indemnified party
                           hereunder, shall contribute to the amount paid or
                           payable by such indemnified party as a result of such
                           loss, liability, claim, damage, or expense in such
                           proportion as is appropriate to reflect the relative
                           fault of the indemnifying party on the one hand and
                           of the indemnified party on the other in connection
                           with the statements or omissions that resulted in
                           such loss, liability, claim, damage, or expense as
                           well as any other relevant equitable considerations.
                           The relative fault of the indemnifying party and of
                           the indemnified party shall be determined by
                           reference to, among other
<PAGE>

                           things, whether the untrue or alleged untrue
                           statement of a material fact or the omission to state
                           a material fact relates to information supplied by
                           the indemnifying party or by the indemnified party
                           and the parties' relative intent, knowledge, access
                           to information, and opportunity to correct or prevent
                           such statement or omission.

                  (v)      Notwithstanding the foregoing, to the extent that the
                           provisions on indemnification and contribution
                           contained in the underwriting agreement entered into
                           in connection with the underwritten public offering
                           are in conflict with the foregoing provisions, the
                           provisions in the underwriting agreement shall
                           control (it being understood and agreed that silence
                           in the underwriting agreement as to matters of
                           indemnification and contribution between the Company
                           and the Holders shall not constitute a conflict).

                  (vi)     The obligations of the Company and Holders under this
                           SECTION 23(i) shall survive the completion of any
                           offering of Registrable Securities in a registration
                           statement under this Warrant Agreement, and
                           otherwise.

         (j)      PERMITTED TRANSFEREES. The rights to cause the Company to
                  register Registrable Securities granted to the Holders by the
                  Company under this Warrant Agreement may be assigned in full
                  by a Holder in connection with a transfer by such Holder of
                  its Registrable Securities if: (i) such Holder gives prior
                  written notice to the Company; (ii) the transferee agrees in
                  writing to comply with the terms and provisions of this
                  Warrant Agreement; (iii) such transfer of Registrable
                  Securities is otherwise in compliance with this Warrant
                  Agreement; and (iv) such transfer of Registrable Securities is
                  otherwise effected in accordance with applicable securities
                  laws. Except as specifically permitted by this SECTION 23(j),
                  the rights of a Holder with respect to Registrable Securities
                  as set out in this SECTION 23 shall not be transferable to any
                  other Person, and any attempted transfer shall cause all
                  rights of such Holder therein to be forfeited.

         (k)      TERMINATION OF REGISTRATION RIGHTS. In addition, the right of
                  any Holder to request inclusion in any registration pursuant
                  to this SECTION 23 and the obligations of the Company to keep
                  any registration statement effective for the benefit of such
                  Holder shall terminate at such time as all of the Registrable
                  Securities held by such Holder may be sold under Rule 144(k)
                  within a 60 day period.

         IN WITNESS WHEREOF, the parties hereto have caused this Agreement to be
         executed by their respective officers thereunto duly authorized as of
         the day and year first above written.

                                  CORNERSTONE PROPANE PARTNERS, L.P.

                                  By:      CORNERSTONE PROPANE GP, INC.
                                           its general partner

                                           By:
                                              ----------------------------------
                                           Name:
                                                --------------------------------
                                           Title:
                                                 -------------------------------
<PAGE>

                            NORTHWESTERN CORPORATION

                                           By:
                                              ----------------------------------
                                           Name:
                                                --------------------------------
                                           Title:
                                                 -------------------------------

<PAGE>

                                                                     EXHIBIT A-1

THE SECURITIES REPRESENTED BY THIS CERTIFICATE HAVE NOT BEEN REGISTERED UNDER
THE SECURITIES ACT OF 1933, AS AMENDED, OR ANY STATE SECURITIES LAWS. SAID
SECURITIES MAY NOT BE SOLD OR TRANSFERRED IN THE ABSENCE OF SUCH REGISTRATION OR
AN EXEMPTION FROM THE REGISTRATION PROVISIONS OF SAID ACT OR LAWS. THE
SECURITIES REPRESENTED BY THIS CERTIFICATE ARE SUBJECT TO THE TERMS OF A WARRANT
AND REGISTRATION RIGHTS AGREEMENT, DATED AS OF JUNE 30, 2000, BETWEEN
CORNERSTONE PROPANE PARTNERS, L.P. (THE "COMPANY") AND NORTHWESTERN CORPORATION,
A COPY OF WHICH IS ON FILE AT THE MAIN OFFICE OF THE COMPANY. ANY SALE OR
TRANSFER OF THE SECURITIES EVIDENCED BY THIS CERTIFICATE IS SUBJECT TO THE TERMS
OF THAT AGREEMENT AND ANY SALE OR TRANSFER OF SUCH SECURITIES IN VIOLATION OF
SAID AGREEMENT SHALL BE INVALID.

Certificate No. __________                                   __________ Warrants

                               Warrant Certificate

                       CORNERSTONE PROPANE PARTNERS, L.P.

              This Warrant Certificate certifies that [______________________],
a _______________corporation (the "PURCHASER"), or its registered assigns, is
the registered holder of the number of Warrants (the "WARRANTS") set forth above
to purchase limited partnership interests of the Company defined as "Common
Units" in the Partnership Agreement and having the rights and obligations
specified with respect to Common Units in the Partnership Agreement (the
"COMMON UNITS"), of CORNERSTONE PROPANE PARTNERS, L.P., a Delaware limited
partnership (the "COMPANY"). Each Warrant entitles the holder upon exercise to
receive from the Company one fully paid and nonassessable Common Unit (a
"WARRANT UNIT") upon the payment by the Purchaser to the Company of the initial
exercise price (the "EXERCISE PRICE") of $0.10, payable in lawful money of the
United States of America, upon surrender of this Warrant Certificate and payment
of the Exercise Price at the office of the Company designated for such purpose,
subject to the conditions set forth herein and in the Warrant Agreement
referenced below. The Exercise Price and number and type of Warrant Units
issuable upon exercise of the Warrants are subject to adjustment upon the
occurrence of certain events, as set forth in the Warrant Agreement.

              The Warrants evidenced by this Warrant Certificate are part of a
duly authorized issue of Warrants, and are issued or to be issued pursuant to a
Warrant and Registration Rights Agreement, dated as of June 30, 2000 (the
"WARRANT AGREEMENT"), which has been duly executed and delivered by the Company
and Northwestern Corporation, which Warrant Agreement is hereby incorporated by
reference in and made a part of this instrument and are hereby referred to for a
description of the rights, obligations and duties hereunder of the Company and
the holders of the Warrants (the words "holders" or "holder" meaning the
registered holders or registered holder). By acceptance of this Warrant
Certificate, the holder hereof agrees to be bound by the Warrant Agreement.
Copies of the Warrant Agreement may be obtained by the holder hereof upon
written request to the Company. The Warrants evidenced by this Warrant
Certificate are exercisable at any time and from time to time during the period
beginning on the date hereof and ending on August 2, 2005 (the "EXPIRATION
DATE").
<PAGE>

              The holder of Warrants evidenced by this Warrant Certificate may
exercise such Warrants under and pursuant to the terms and conditions of the
Warrant Agreement by surrendering this Warrant Certificate, with the form of
election to purchase attached hereto (and by this reference made a part hereof)
properly completed and executed, together with payment of the Exercise Price in
cash at the office of the Company designated for such purpose. In the event that
any exercise of Warrants evidenced hereby shall be for less than the total
number of Warrants evidenced hereby and except as otherwise provided in the
Warrant Agreement, there shall be issued by the Company to the holder hereof or
its registered assignee a new Warrant Certificate evidencing the number of
Warrants not exercised.

              The Warrant Agreement provides that upon the occurrence of certain
events the Exercise Price set forth on the face hereof and the number of Warrant
Units issuable upon the exercise of each Warrant may, subject to certain
conditions, be adjusted. No fractional Warrant Units will be issued upon the
exercise of any Warrant, but the Company will pay the cash value thereof
determined as provided in the Warrant Agreement.

              Warrant Certificates, when surrendered at the office of the
Company by the registered holder thereof in person or by legal representative or
attorney duly authorized in writing, may be exchanged, in the manner and subject
to the limitations provided in the Warrant Agreement, for another Warrant
Certificate or Warrant Certificates of like tenor evidencing in the aggregate a
like number of Warrants.

              The Company may deem and treat the registered holder(s) thereof as
the absolute owner(s) of this Warrant Certificate (notwithstanding any notation
of ownership or other writing made hereon) for the purpose of any exercise
hereof, of any distribution to the holder(s) hereof and for all other purposes,
and the Company shall not be affected by any notice to the contrary. Neither the
Warrants nor this Warrant Certificate entitles any holder hereof to any rights
of a limited partner of the Company.

<PAGE>

              IN WITNESS WHEREOF, the Company has caused this Warrant
Certificate to be signed by its duly authorized officer and has caused its
corporate seal to be affixed hereunto or imprinted hereon.

Dated:
      ------------------------------------
         CORNERSTONE PROPANE PARTNERS, L.P.

                                  By:      CORNERSTONE PROPANE GP, INC.
                                           its general partner

                                           By:
                                              ----------------------------------
                                           Name:
                                                --------------------------------
                                           Title:
                                                 -------------------------------

[CORPORATE SEAL]<PAGE>
                                                                     EXHIBIT 4.4

                                             DANIEL K. NEWELL
                                             EXECUTIVE VICE PRESIDENT-FINANCE
                                             DIRECT:  (605) 978-2965
                                             CELL:  (954) 629-2123

[NORTHWESTERN CORPORATION LETTERHEAD]

                                  June 28, 2000

CornerStone Propane Partners, L.P.
432 Westridge Drive
Watsonville, CA  95076

Attention:        Mr. Keith G. Baxter
                  President and Chief Financial Officer

Dear Keith:

You have advised NorthWestern Corporation, a Delaware corporation ("NOR"), that
CornerStone Propane, L.P. (the "OLP"), a subsidiary of CornerStone Propane
Partners, L.P. (the "MLP", and collectively with all of its subsidiaries,
"CNO"), desires to amend (the "Amendment") its credit facility, the Refunding
Credit Agreement dated as of November 20, 1998, among the OLP, Bank of America
as Agent, and the Bank Lenders named therein (the "Credit Agreement"). In
connection therewith, you have requested that NOR provide certain credit support
("Credit Support") for the OLP in favor of the Bank Lenders.

You have advised us that the Credit Support is a condition precedent to the
execution of the Amendment by the Bank Lenders. You also have advised us that
the Summary of Terms and Conditions and Indemnification, attached hereto as
EXHIBIT A and EXHIBIT B, respectively, which are incorporated into and made a
part of this Commitment Letter, have been approved by the independent Audit
Committee of the Board of Directors of the MLP's General Partner. I am pleased
to advise you that NOR hereby commits (the "Commitment") that it or one of its
affiliates will provide, subject to the terms and conditions set forth herein,
the Credit Support described in the Summary Terms and Conditions attached hereto
as EXHIBIT A. You understand that our commitment to make the Credit Support
available to CNO is subject expressly to the execution and delivery of
definitive documentation, including without limitation a definitive First
Amendment, Guaranty Agreement, Warrant Agreement, Registration Rights Agreement
and other documentation satisfactory to us and covering the matters expressly
referred to herein and covering such other matters as we may reasonably request
(collectively, the "Definitive Documents") and satisfaction of the other
conditions precedent set out in the Summary of Terms and Conditions.

CNO agrees to pay to NOR (or its designated affiliate) the fees set forth in the
Summary Terms and Conditions, including without limitation, the commitment fee
(the "Commitment Fee") in an amount equal to $3,055,000 (6.50%) of the aggregate
amount of the $47 million in Credit Support. CNO also agrees to pay to NOR a
takedown fee ("Take-Down Fee") in an amount equal to 3% of the actual funds
advanced.
<PAGE>

The Commitment Fee will be earned and payable upon acceptance of this
Commitment. The Takedown Fee will be earned and payable upon the advance of
funds pursuant to the Credit Support.

The Commitment is not assignable by you. Nothing in this Commitment Letter,
expressed or implied, shall give any person, other than the parties hereto, any
benefit or any legal or equitable right, remedy or claim under this Commitment
Letter.

CNO agrees to indemnify and hold NOR (and its affiliates), harmless to the
extent set forth in EXHIBIT B to this Commitment Letter and, upon demand from
time to time, to reimburse NOR (and its affiliates), for all reasonable
out-of-pocket costs, expenses and other payments, including but not limited to
legal fees and disbursements incurred or made in connection with the Commitment,
and the preparation, execution and delivery of the Definitive Documents,
regardless of whether or not the Definitive Documents are executed.

This Commitment Letter, the attached Summary of Terms and Conditions, and terms
of indemnification set forth the entire understanding of the parties as to the
scope of the Commitment and NOR's obligations hereunder. This Commitment will
expire at 5:00 PM pacific time on June 30, 2000, unless accepted prior to such
time. This Commitment will also expire on the termination of the Credit
Agreement.

This Commitment Letter shall be governed by, and construed in accordance with,
the laws of the State of New York as applied to contracts made and performed
within such state, without giving effect to the principles of conflicts of laws
thereof. To the fullest extent permitted by applicable law, each of CNO and NOR
hereby irrevocably submit to the jurisdiction of any New York State court or
Federal court sitting in the Borough of Manhattan in New York City in respect of
any suit, action or proceeding arising out of or relating to the provisions of
the Commitment and irrevocably agree that all claims in respect of any such
suit, action or proceeding may be heard and determined in any such court. Each
of NOR and CNO waive, to the fullest extent permitted by applicable law, any
objection which it may now or hereafter have to the laying of the venue of any
such suit, action or proceedings brought in any such court, and any claim that
any such suit, action or proceeding brought in any such court has been brought
in an inconvenient forum. Each of CNO and NOR hereby irrevocably waives, to the
fullest extent permitted by law, any and all right to trial by jury in any legal
proceeding arising out of or relating to the matters set forth herein.

Please indicate your acceptance of our Commitment and your agreement to the
matters contained in this Commitment Letter and the attached EXHIBIT A and
EXHIBIT B by executing this document and returning it to us prior to the time of
expiration set forth above.

                                      Sincerely,

                                      NorthWestern Corporation

                                      Daniel K. Newell
                                      Executive Vice President - Finance
<PAGE>

Accepted and Agreed to as of June 30, 2000:

CornerStone Propane Partners, L.P.
By:                    CornerStone Propane, G.P.,
                                  General Partner

By:
       -----------------------------------

Title:
       -----------------------------------

<PAGE>

                                                                       EXHIBIT A

                         SUMMARY OF TERMS AND CONDITIONS

Set forth below is a summary of the terms and conditions of the credit support
that NorthWestern Corporation ("NOR") (or an affiliate) would consider providing
to CornerStone Propane Partners, L.P. ("CNO"), consisting of a guaranty of
certain obligations of CornerStone Propane, L.P. (the "OLP") under the Refunding
Credit Agreement, dated November 20, 1998, among the OLP, Bank of America, as
Agent, and the Lenders party thereto (the "Credit Agreement").

CREDIT GUARANTY:

Borrower:                  CornerStone Propane, L.P. (the "OLP").

Guarantor:                 NorthWestern Corporation (or an affiliate) (the
                           "Guarantor").

Obligations:               Advances under the Refunding Credit Agreement, dated
                           November 20, 1998, among the OLP, Bank of America, as
                           Agent, and the Lenders party thereto (the "Credit
                           Agreement").

Guaranteed Amount:         Up to $47,000,000 (or such lesser amount as CNO may
                           request) of Advances under the Credit Agreement.

Subrogation:               Guarantor to receive full and customary rights of
                           subrogation from the Lenders, including, without
                           limitation, prorata rights in the proceeds of
                           collateral subject to the Intercreditor and Trust
                           Agreement, dated as of December 11, 1996, as amended,
                           among the OLP, the Lenders under the Credit
                           Agreement, and the holders of OLP Senior Secured
                           Notes (the "Intercreditor Agreement").

Guaranty Fee:              A fee of 6.50% per annum on the total guaranty
                           commitment, payable in advance.

Guaranty Payments:         Upon demand of Credit Agreement Lenders upon payment
                           default, acceleration of loans or failure to pay at
                           stated maturity as provided in the form of guaranty.

Terms of Advances:         If Guarantor is required to advance funds as payment
                           under the Guaranty, the following terms and
                           conditions shall apply:

Due Date:                  The advances shall be due and payable by the OLP
                           immediately on demand.
<PAGE>

Interest Rate:             Interest on outstanding advances shall be charged
                           at LIBOR plus a designated spread until the date
                           of repayment. The spread will initially be 9%. If
                           the advances are not repaid in full with interest
                           on or prior to the three month anniversary of the
                           date of the first advance (the "Advance Date"),
                           the spread will increase by an additional 100
                           basis points and shall continue to increase by an
                           additional 50 basis points at the end of each
                           subsequent three month period for so long as the
                           advances remain outstanding.

Interest Payments:         Quarterly in arrears.

PIK Feature:               Interest payments, at the sole election of
                           Guarantor, may be paid through the issuance of
                           MLP Common Units (valued at the closing price on
                           the date of issue).

ADDITIONAL TERMS AND CONDITIONS:

Take Down Fee:             If Guarantor is required to advance funds under the
                           Guaranty, a take-down fee equal to 3% of the actual
                           funds advanced shall be charged, payable on date of
                           funding.

Expenses:                  Reasonable fees and expenses incurred by Guarantor in
                           connection with documenting and providing the credit
                           support described herein, including, without
                           limitation, the fees and disbursements of counsel and
                           fees and charges imposed by the bank group, and
                           related amendment and/or enforcement costs shall be
                           paid by CNO.

Indemnification:           Customary lender indemnification..

Equity Warrants:           At the closing, CNO shall issue 5-year warrants to
                           purchase 325,000 MLP Common Units, immediately
                           exercisable at an exercise price of $0.10 per unit.

Registration Rights:       Demand and piggy-back registration rights on
                           customary terms for any Common Units received as PIK
                           interest or upon exercise of equity warrants.

Approvals:                 All arrangements subject to approval by the NOR Board
                           of Directors and the independent Audit Committee of
                           the Board of Directors of CNO GP; approval by CNO GP
                           Board of revised operating plan and projections;
                           approval by Guarantor of terms of amendment to Credit
                           Agreement and related guaranty documentation; third
                           party consents; and other customary conditions.

Governing Law:             New York.

<PAGE>

                                                                       EXHIBIT B

                                 INDEMNIFICATION

In consideration of the commitment given by NorthWestern Corporation, a Delaware
Corporation ("NOR"), to CornerStone Propane Partners, L.P. ("CNO" or the
"Indemnifying Party") pursuant to the Commitment Letter between CNO and NOR of
which this Exhibit is a part (such Commitment Letter, together with the Summary
Terms and Conditions attached thereto and this Exhibit, is referred to herein as
the "Commitment"), CNO agrees to indemnify and hold harmless NOR, it affiliates,
and each person, if any, who controls NOR, or any of its affiliates, within the
meaning of the Securities Act of 1933, as amended (the "Act") or the Securities
Exchanges Act of 1934, as amended (a "Controlling Person"), and the respective
partners, agents, employees, officers and directors of NOR, its affiliates, and
any such Controlling Person (each an "Indemnified Party" and collectively, the
"Indemnified Parties" or the "NOR Group"), from and against any and all losses,
claims, damages, liabilities and expenses (including, without limitation and as
incurred, reasonable costs of investigating, preparing or defending any such
claim or action, whether or not NOR Group is a party thereto) arising out of, or
in connection with any activities contemplated by, the Commitment or any other
services rendered in connection therewith, provided that CNO will not be
responsible for any claims, liabilities, losses, damages or expenses that are
determined by final judgment of a court of competent jurisdiction to result
solely from NOR Group's gross negligence, willful misconduct or bad faith. CNO
also agrees that NOR Group shall have no liability (except for breach of
provisions of the Commitment Letter for which this EXHIBIT B is a part) for
claims, liabilities, damages, losses or expenses, including legal fees, incurred
by CNO unless they are determined by final judgment of a court of competent
jurisdiction to result solely from NOR Group's gross negligence, willful
misconduct or bad faith.

In case any action shall be brought against NOR Group with respect to which
indemnity may be sought against CNO under this agreement, NOR Group shall
promptly notify CNO in writing and CNO shall, if requested by NOR, assume the
defense thereof, including the employment of counsel satisfactory to NOR and
payment of all reasonable fees and expenses. The failure to so notify CNO shall
not affect any obligations CNO may have to NOR Group under this Commitment or
otherwise unless CNO is materially adversely affected by such failure. NOR Group
shall have the right to employ separate counsel in such action and participate
in the defense thereof, but the fees and expenses of such counsel shall be at
the expense of NOR Group, unless: (i) CNO has failed to assume the defense and
employ counsel satisfactory to NOR or (ii) the named parties to any such action
(including any impleaded parties) include NOR Group and CNO, and NOR Group shall
have been advised by counsel that there may be one or more legal defenses
available to it which are different from or additional to those available to
CNO, in which case, if such Indemnified Party notifies the Indemnifying Party in
writing that it elects to employ separate counsel at the expense of the
Indemnifying Party, the Indemnifying Party shall not have the right to assume
the defense of such action or proceeding on behalf of such Indemnified Party,
provided, however, that CNO shall not, in connection with any one such action or
proceeding or separate but substantially similar or related actions or
proceedings in the same jurisdiction arising out of the same general allegations
or circumstances, be responsible hereunder for the reasonable fees and expenses
of more than one such firm of separate counsel, in additional to any local
counsel, which counsel shall be designated by NOR. CNO shall not be liable for
any settlement of any such action effected without the written consent of CNO
(which shall not be unreasonably withheld) and CNO agrees to indemnify and hold
harmless NOR Group from and against any loss or liability by reasons of
settlement of any action effected with the consent of CNO. In addition, CNO will
not, without the prior written consent of NOR, settle or compromise or consent
to the entry of any judgment in or otherwise seek to terminate any pending or
threatened action, claim, suit or proceeding in respect to which indemnification
or contribution may be sought hereunder
<PAGE>

(whether or not NOR is a party thereto) unless such settlement, compromise,
consent or termination includes an express unconditional release of NOR Group
and the other Indemnified Parties, satisfactory in form and substance to NOR,
from all liability arising out of such action, claim, suit or proceeding.

If for any reason the foregoing indemnity is unavailable to an Indemnified Party
or insufficient to hold an Indemnified Party harmless, then in lieu of
indemnifying such Indemnified Party, CNO shall contribute to the amount paid or
payable by such Indemnified Party as a result of such claims, liabilities,
losses, damages, or expenses (i) in such proportion as is appropriate to reflect
the relative benefits received by CNO on the one hand and by NOR on the other
from the transaction contemplated by this Commitment or (ii) if the allocation
provided by clause (i) is not permitted under applicable law, in such proportion
as is appropriate to reflect not only the relative benefits received by CNO on
the one hand and NOR on the other, but also the relative fault of CNO and NOR as
well as any other relevant equitable considerations. Notwithstanding the
provisions of this EXHIBIT B, the aggregate contribution of all Indemnified
Parties shall not exceed the amount of fees actually received by NOR pursuant to
the Commitment. It is hereby further agreed that the relative benefits to CNO on
the one hand and NOR on the other with respect to any Transaction shall be
deemed to be in the same proportion as (i) the total value of the transaction
bears to (ii) the fees paid to NOR with respect to such transaction. No
Indemnified Party shall have any liability to CNO or any other person in
connection with the services rendered pursuant to the Commitment except for the
liability for claims, liabilities, losses or damages finally determined by a
court of competent jurisdiction to have resulted from action taken or omitted to
be taken by such Indemnified Party in bad faith or to be due to such Indemnified
Party's willful misconduct, or gross negligence.

The indemnity, contribution and expense reimbursement obligations set forth
herein (i) shall be in addition to any liability CNO may have to any Indemnified
Party at common law or otherwise, (ii) shall survive the termination of the
Commitment and (iii) shall remain operative and in full force and effect
regardless or any investigation made by or on behalf of the NOR or any other
Indemnified Party.

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