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Exhibit 10.1(i)

RETIREMENT AGREEMENT

        This RETIREMENT AGREEMENT (this "Agreement") is effective as of the 31st
day of December, 2002 (the "Effective Date"), between NorthWestern Corporation,
a Delaware corporation (the "Company"), and Merle D. Lewis ("Executive").

Recitals

        WHEREAS, the Company and Executive are parties to a certain
Comprehensive Employment Agreement and Investment Program, dated June 1, 2000
(including the Change of Control Agreement attached thereto as Schedule E and
the Noncompetition Agreement attached thereto as Schedule F, and the other
schedules attached thereto, the "Employment Agreement"), pursuant to which
Executive currently serves as the Company's Chief Executive Officer and
Chairman.

        WHEREAS, Executive desires to retire from the Company.

        WHEREAS, the Company and Executive desire to terminate the Employment
Agreement and that Executive resigns as the Company's Chief Executive Officer
and Chairman, in accordance with the terms and conditions of this Agreement.

        WHEREAS, the Company and Executive also desire that Executive resigns as
a member of the Board of Directors (the "Board") of the Company, as a trustee or
other administrator of any benefit or pension plans of the Company or any of its
subsidiaries or affiliates (other than as a member of the board of directors of
CornerStone Propane G.P., Inc.), and as an officer and director of each of the
Company's subsidiaries and affiliates for which he so serves, in accordance with
the terms and conditions of this Agreement.

        NOW THEREFORE, in consideration of the mutual covenants set forth
herein, and for other good and valuable consideration, the receipt and
sufficiency of which are hereby acknowledged, the parties hereto hereby agree as
follows:

Terms of Agreement

        1.    Termination of Employment Agreement.    As of the Effective Date,
the Employment Agreement shall terminate (without regard to Section 4
(Termination) thereof) and no longer have any legal force or effect, and neither
party shall have any obligation or liability to the other thereunder either as a
result of such termination or otherwise, except that (a) Section 5 (Proprietary
Information Obligations), Section 6 (Covenant Not to Compete), including
Schedule F, Section 7 (Arbitration of Disputes) (without regard to the second
sentence of subsection (d)), and Section 8 (Indemnification) of the Employment
Agreement and (b) the Noncompetition Agreement entered into between the parties
on June 1, 2000 and attached thereto are hereby incorporated by reference into
this Agreement and shall continue in this Agreement in full force and effect as
if fully set forth herein, and the parties hereto shall have the right to
enforce such provisions under this Agreement as to all claims each may have
under such provisions or agreements from the date such agreements were initially
entered into (i.e., June 1, 2000).

        2.    Retirement and Resignation.    Executive hereby retires from his
employment with the Company and its subsidiaries and affiliates effective as of
the Effective Date. Executive hereby resigns as the Company's Chief Executive
Officer and Chairman and from all trustee, administrator or similar positions in
which he now serves on behalf of the Company or any of its subsidiaries or
affiliates (including in respect of any benefit or pension plans of any of the
foregoing), effective as of the Effective Date. Executive further hereby resigns
as a member of the Board, and as an officer and director of each of the
Company's subsidiaries and affiliates (other than as a member of the board of
directors of CornerStone Propane G.P., Inc.) for which he so serves, effective
as of the Effective Date. Executive acknowledges that the Company has the right
(and has reserved such right) to remove any or

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all of the members of the board of directors of CornerStone Propane Partners,
L.P., including Executive, and Executive will resign from the board of
CornerStone Propane G.P., Inc. immediately upon the request of the Company.
Executive acknowledges and agrees that the resignation pursuant to this
Section 2 shall not be deemed to be a termination (whether for or without cause
or otherwise) under Section 4 of the Employment Agreement.

        3.    Benefits.    Subject to any withholding obligation set forth in
Section 5.2, the Company shall provide Executive with the following:

        3.1    Cash Payments.    Subject to applicable law and in no event later
than five (5) days after the execution and delivery of this Agreement, the
Company shall deliver to Executive, by check or wire transfer to an account
designated by Executive, an amount equal to One Million Two Hundred Eleven
Thousand Dollars ($1,211,000). No later than eight (8) days after the execution
and delivery of this Agreement, the Company shall deliver to Executive, by check
or wire transfer to an account designated by Executive, an additional amount
equal to Five Hundred Thousand Dollars ($500,000); provided, that if Executive
revokes the Release (as defined in Section 6.1) in respect of any Claims (as
defined in Section 6.1) Executive may have under the Age Discrimination in
Employment Act within seven (7) days after the execution and delivery of this
Agreement, the Company shall not be required to pay such amount to Executive. If
the date on which any payment pursuant to this Section 3.1 is due is not a
business day, then the Company shall pay the amount due on the next succeeding
business day.

        3.2    Compensation and Benefit Plans.    

        (a)    Accrued Vacation Pay.    No later than February 7, 2003, the
Company shall pay Executive for all accrued, but unused vacation time as of the
Effective Date, up to a maximum of twenty (20) vacation days; it being
understood that any such payment shall be calculated using Executive's base
salary as of the Effective Date.

        (b)    Vesting of Restricted Stock.    Promptly following the execution
and delivery of this Agreement, Executive shall be fully vested in the 22,511
shares of Restricted Stock granted to Executive on March 1, 2001 (together with
all additional shares purchased with dividends declared thereon) under the
Company's Stock Option and Incentive Plan (as amended on January 16, 2001, the
"Plan"), and all restrictions on such shares contained in the Plan or in the
Restricted Stock Purchase Agreement shall be removed, except that Executive
shall continue to be obligated to comply with all applicable securities laws in
respect of the sale of such securities including, without limitation, trading in
accordance with Company policy, the Securities Act of 1933, as amended, and
Section 16 of the Securities Exchange Act of 1934, as amended. The Company shall
furnish Executive with a memorandum of counsel outlining the compliance
obligations referenced in this section. Except as set forth above, Executive
hereby surrenders, releases, disavows, and waives any and all rights, benefits,
payments or other interests he may have under the Plan.

        (c)    NorthWestern Energy Corporation Equity Ownership Incentive
Plan.    The Company shall pay to Executive no later than eight (8) days
following the execution and delivery of this Agreement, in accordance with the
1998 NorthWestern Energy Corporation Equity Ownership Incentive Plan (the "NEC
Plan"), all interest earned by Executive under the NEC Plan, in the amount of
Seventy Three Thousand Dollars ($73,000); provided, that if the date on which
the payment pursuant to this Section 3.2(c) is due is not a business day, then
the Company shall pay the amount due on the next succeeding business day. Except
as set forth above, Executive hereby surrenders, releases, disavows, and waives
any and all rights, benefits, payments or other interests he may have under the
NEC Plan.

        (d)    Retirement Health Insurance Plan.    Executive shall be permitted
to participate in the Company's retiree health insurance plan in accordance with
the terms and conditions of such plan

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and will receive Five Hundred Dollars ($500) per month, from the Effective Date
until the month in which Executive reaches age sixty five (65).

        (e)    Retention of Company Car.    Executive shall be permitted to
retain for his personal use, through the end of the current lease, the
automobile currently leased for him by the Company, and the Company shall
continue to pay the remaining payments under the current lease, subject to
Executive maintaining reasonable insurance coverage naming the Company as an
additional insured. Executive shall provide the Company with proof of such
insurance. Executive shall be solely responsible for the condition of the
automobile. Executive shall surrender the automobile to the lessor upon
expiration or termination of the lease and shall pay all amounts or charges then
due or payable, including charges with respect to vehicle condition or mileage
(provided, that Executive may elect to purchase the vehicle, extend the lease or
enter into some other arrangement with the lessor provided that there shall be
no additional charge or expense to the Company).

        (f)    Retention of Vested Benefits.    Executive shall be permitted to
retain all benefits vested or earned as of the Effective Date in the plans
listed on Exhibit A hereto; it being understood that Executive shall not be
entitled to participate in such plans after the Effective Date and that no
further vesting of benefits or interests in such plans by Executive shall occur
from and after the Effective Date (other than as specifically provided in this
Agreement).

        (g)    Additional Pension Benefit.    Executive shall be entitled to all
benefits vested or earned as of the Effective Date under the plans listed on
Exhibit B hereto, in each case as further amended by the Company (collectively,
the "Pension Plans"), to the extent, but only to the extent, permitted by and
subject to the terms and conditions of, the Pension Plans and applicable law;
provided, that to the extent allowable under the terms of the Pension Plans
(without the imposition of conditions that are, in the reasonable and good faith
judgment of the Company, materially adverse to the Company or the maintenance of
the Pension Plans), Executive's benefits earned or amounts payable under each of
the Pension Plans shall be calculated as if Executive's term of service or
employment with the Company terminated on and as of June 30, 2006 (the "Adjusted
Benefit Date"), regardless of the actual date of retirement or payment of such
benefits. Executive's interest in the Pension Plans shall cease to vest from and
after the Effective Date. To the extent that Executive's benefits under the
Pension Plans, or any of them, can not be reasonably increased (as determined in
the Company's sole discretion) to give effect to the Adjusted Benefit Date, then
the Company shall pay such additional amounts to Executive as necessary to give
such effect, and such additional payments by the Company shall be made at the
same time and in the same manner as payments under the Pension Plans. Without
limiting the foregoing, (A) Executive's benefits under the Pension Plans shall
remain subject to reduction or other limitation for early retirement and (B) the
Company may, in its sole discretion, elect to pay all benefits resulting from
consideration of the Adjusted Benefit Date rather than amending or revising the
Pension Plans, or any of them. Pension benefits for Executive shall commence
effective January 1, 2003 and continue on a monthly basis in accordance with the
provisions of the Pension Plans. Initial monthly benefit amounts are estimated
to be $29,146 based on the selection of the Ten (10) Year Certain and Continuous
Option of benefit payments.

        4.    Cancelled Rights and Benefits; Assignment of Interest.    

        4.1    Cancellation of Rights and Benefits.    Except as specifically
provided in this Agreement, Executive hereby surrenders, releases, disavows, and
waives any rights, benefits, payments or other interests to which he may be
entitled as an officer, director, employee or agent of the Company or under the
Employment Agreement, including, but not limited to, the following:

        (a)    Vested and Unvested Options.    All vested and unvested incentive
stock options and non-qualified stock options granted to Executive under the
Plan;

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        (b)    Cancellation of Phantom Stock Units.    All Phantom Stock Units
(including all dividends accrued thereon) granted to Executive under the Plan;

        (c)    Equity Ownership Incentive Plans for NorthWestern Growth
Corporation, NorthWestern Services Group, Inc., NorthWestern Public Service,
North Western Services Corporation, and NorCom Advanced
Technologies, Inc.    All rights, benefits, payment obligations (to the
participants by such plans), ownership interests, or other rights arising out of
or related to equity ownership incentive plans for NorthWestern Growth
Corporation, NorthWestern Services Group, Inc., NorthWestern Public Service,
North Western Services Corporation, and NorCom Advanced Technologies, Inc.;

        (d)    Annual Incentive Plans.    All rights, benefits, payments or
other interests arising out of or related to Annual Incentive Plans for the
Company and any of its subsidiaries, divisions, and affiliates for the year
2002;

        (e)    Disability Plans.    All short-term and long-term disability
insurance coverage provided to Executive by the Company;

        (f)    Term Life Insurance.    All term life insurance coverage provided
to Executive by the Company; and

        (g)    Other Benefits.    All other benefits provided to Executive by
the Company, including, without limitation, the payment by the Company of
business expense reimbursement, country club dues, social dues, and association
dues, and the provision by the Company of secretarial support and office space.

        4.2    Assignment of Interest in NorthWestern Capital Partners,
LLC.    Executive hereby sells, transfers, and assigns to the Company all of his
right, title and interest in and to the membership interests of NorthWestern
Capital Partners, LLC, a Delaware limited liability company ("NWCP, LLC"), and
shall have no further interests or rights as a member of NWCP, LLC. Executive
shall take such further action as necessary to amend the operating agreement of
NWCP, LLC to effectuate the foregoing.

        5.    Other Covenants.    

        5.1    Return of Company Property.    No later than five (5) days after
the Effective Date, Executive shall return to the Company all files (including
computer files), memoranda, documents, records (including all electronic
records), building passes, and keys (including all copies of the foregoing), and
all credit cards and other property belonging to the Company or any of its
affiliates that are in Executive's possession; provided, that Executive shall
not be required to return the following items that have previously been provided
to him by the Company: (a) personal computing equipment; (b) cell phone;
(c) printer; and (d) fax machine; provided further, that Executive shall bear
all monthly service fees and other costs and fees associated with the items
listed in clauses (a) through (d) above from and after the Effective Date, and
the Company shall be permitted to cancel such services or to transfer such
services to Executive's name. Executive shall also be entitled to keep the
personal computer provided to him by the Company, and within five (5) days of
the Effective Date Executive and the Company shall use reasonable efforts to
delete all Company records from such computer. If such records cannot be deleted
to the Company's reasonable satisfaction, the Company shall exchange with
Executive Executive's current computer for a computer of like model and
condition.

        5.2    Taxes.    Executive shall be responsible for paying any and all
taxes on amounts payable to him under this Agreement and acknowledges that the
Company will withhold all taxes it determines are legally required to be
withheld under applicable federal and state law. Executive further agrees not to
make any claim against the Company or any other person based on how the

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Company reports amounts paid under this Agreement to the tax authorities of any
jurisdiction or if an adverse determination is made as to the tax treatment of
any amounts payable under this Agreement. In addition, Executive understands and
agrees that the Company has no duty to attempt to prevent such an adverse
determination.

        5.3    No Disparagement or Harm.    For a period of ten (10) years after
the Effective Date, (a) Executive shall not criticize, denigrate or disparage
any Released Party (as defined in Section 6.1 below) in any manner and (b) the
Company shall not publicly criticize, denigrate or disparage Executive in any
manner.

        5.4    Cooperation.    As further consideration for the covenants set
forth herein, Executive hereby agrees to cooperate fully with the Company and
any lawyer, law firm, or consultant that the Company designates from time to
time with respect to any litigation, deposition, hearing, arbitration or other
proceeding involving the Company. Such cooperation shall include, without
limitation, support of the Company's position in defending any employment
related lawsuits or claims in respect of which Executive has knowledge, or any
audits, investigations, lawsuits, complaints, or proceedings by government
entities or stockholders (whether brought directly or derivatively). Executive
shall not seek any compensation or fee in excess of the actual and reasonably
necessary expenses incurred with respect to such cooperation. Executive further
covenants that he will contact the Company's Legal Department in the event that
there is any subpoena, notice or other instruction directing Executive to appear
in any legal proceeding involving the Company.

        5.5    Payment Guarantee.    In the event of a Change of Control (as
defined below) of the Company, upon the written request of Executive the Company
shall promptly secure the payments required by this Agreement in respect of the
nonqualified portion of the Pension Plans by promptly delivering to Executive a
fully paid and non-cancelable annuity, irrevocable letter of credit or other
financial instrument bearing financial, interest rate return and payment terms
reasonably acceptable to Executive. The term "Change of Control" means any
transaction or series of related transactions (including, without limitation, a
reorganization, merger, consolidation, or other business combination) in which
(a) the Company sells all or substantially all of its assets, (b) a person or
group (as used in Section 13 of the Securities Exchange Act of 1934, as amended)
acquires fifty percent (50%) or more of the Company's outstanding voting power
or (c) the stockholders of the Company immediately prior to such transaction or
series of related transactions do not own more than fifty percent (50%) of the
outstanding voting power of the successor entity immediately after such
transaction or series of related transaction.

        5.6    Press Release.    The parties agree that following the execution
and delivery of this Agreement, the Company shall issue a press lease in the
form set forth on Exhibit C hereto.

        6.    Release.    

        6.1    General.    Executive hereby irrevocably and unconditionally
releases all known and unknown claims, promises, causes of action or similar
rights of any kind or nature (collectively, "Claims") that he may have against
any Released Party (as defined below) in connection with his employment with the
Company or as a stockholder of the Company, other than (a) Executive's right to
enforce this Agreement, (b) any rights or claims that arise after the Effective
Date, and (c) any Claims for indemnification from the Company or any Claims
under the Company's D&O insurance policies, in either case, for actions or
omissions in his capacity as an officer or director of the Company (the
"Release"). The term "Released Party" means the Company and its affiliates and
subsidiaries and their successors and assigns, and each of their respective
officers, directors, stockholders, representatives, attorneys, agents, employee
benefit programs (and the trustees, administrators, fiduciaries, and insurers of
such programs) and any other persons acting by, through, or in concert with, any
of the foregoing.

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        6.2    Acknowledgements.    

        (a)    Executive acknowledges and agrees that the Claims released by him
pursuant to Section 6.1 might arise under many different laws, including but not
limited to:

(i)anti-discrimination statutes, such as the Age Discrimination in Employment
Act and Executive Order 11,141, which prohibit age discrimination in employment;

(ii)other anti-discrimination statutes, such as Title VII of the Civil Rights
Act of 1964, Sections 1981 and 1983 of the Civil Rights Act of 1866, and
Executive Order 11,246, which prohibit discrimination based on race, color,
national origin, religion, or sex; the Equal Pay Act, which prohibits paying men
and women unequal pay for equal work; the Americans With Disabilities Act and
Sections 503 and 504 of the Rehabilitation Act of 1973, which prohibit
discrimination based on disability; and any other federal, state, or local laws
prohibiting employment discrimination;

(iii)federal employment statutes, such as the WARN Act, which requires that
advance notice be given of certain work force reductions; the Employee
Retirement Income Security Act of 1974, which, among other things, protects
employee benefits; the Fair Labor Standards Act of 1938, which regulates wage
and hour matters; the Family and Medical Leave Act of 1993, which requires
employers to provide leaves of absence under certain circumstances; and any
other federal laws relating to employment, such as veterans' reemployment rights
laws; and

(iv)insofar as such Claims relate to Executive's rights as a stockholder only,
any federal or state securities laws, and any federal or state laws establishing
fiduciary duties, duties of loyalty, or similar duties; and

(v)other laws, such as any federal, state, or local laws providing workers'
compensation benefits, restricting an employer's right to terminate employees,
or otherwise regulating employment; any federal, state, or local law enforcing
express or implied employment contracts or requiring an employer to deal with
employees fairly or in good faith; any other federal, state, or local laws
providing recourse for alleged wrongful discharge, tort, physical or personal
injury, emotional distress, fraud, negligent misrepresentation, defamation, and
similar or related claims.

        (b)    Unknown Claims.    Executive understands, acknowledges and agrees
that he is hereby releasing Claims about which he may not currently have
knowledge, even though he may learn that some or all of the facts he currently
believes to be true are untrue and even though he might then regret having
granted the Release. Executive further understands, acknowledges and agrees that
he is assuming that risk and that the Release shall remain effective in all
respects in any such case. Executive expressly waives all rights he might have
under any law that are intended to protect him from waiving unknown claims and
understands the significance of doing so.

        6.3    Consideration of Release.    Executive acknowledges and agrees
that the Company has advised him to take the release set forth in
Section 6.2(a)(i) (the "ADEA Release") home, to read it, and to carefully
consider all of its terms before signing it, and has given Executive at least
twenty-one (21) days in which to consider the ADEA Release. Executive hereby
waives any right he may have to additional time beyond this consideration period
within which to consider the ADEA Release. Executive understands that he has
seven (7) days after he signs the ADEA Release to revoke it. If Executive
chooses to revoke the ADEA Release, he agrees to provide such revocation in
writing to the Senior Vice President, General Counsel, by the end of the seven
(7) day period. Executive acknowledges and agrees that (a) the Company, in
writing, has advised Executive to discuss the ADEA Release with his own attorney
(at his own expense) during this

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seven (7) day period if he wishes to do so, (b) he has carefully read the ADEA
Release, fully understands what it means, and is entering into it voluntarily,
and (c) is receiving valuable consideration in exchange for his execution of the
ADEA Release that he would not otherwise be entitled to receive.

        6.4    Ownership of Claims.    Executive hereby represents and warrants
to the Company that he has not assigned or transferred in any manner any Claim
purported to be released pursuant to this Section 6.

        6.5    Pursuit of Released Claims.    Executive has not filed or caused
to be filed any lawsuit, complaint, or charge with respect to any Claim the
Release purports to waive, and shall not, nor cause another to, file or
prosecute a lawsuit, complaint, or charge based on such Claims. In addition,
Executive shall not seek any damages, remedies, or other relief by filing or
prosecuting a charge with any administrative agency with respect to any such
Claim, and shall request any administrative agency or other body assuming
jurisdiction in any such lawsuit, complaint or charge to withdraw from the
matter or dismiss the matter with prejudice.

        7.    General.    

        7.1    No Admission of Liability.    Each party acknowledges and agrees
that the entering into of this Agreement by the other is not an admission of
guilt or wrong doing by such party (including, in the case of the Company, any
Released Party).

        7.2    Governing Law.    This Agreement shall be governed by, and
construed in accordance with, the laws of the State of Delaware, without
reference to conflict of laws principles thereof.

        7.3    Further Assurances.    Each party agrees to take all further
actions and to execute and deliver all further documents and instruments that
are reasonably necessary or appropriate in order to effectuate the purposes of
this Agreement and the transactions contemplated hereby.

        7.4    Severability.    In the event any provision of this Agreement is
held void or unenforceable by any court of competent jurisdiction, then such
provision shall be severable and shall not affect the validity and
enforceability of the remaining provisions hereof.

        7.5    Waiver.    Any failure by a party hereto to comply with any
obligation, agreement or condition contained herein may only be waived in a
writing executed by the party granting the waiver, but such waiver or failure to
insist upon strict compliance with such obligation, agreement or condition shall
not operate as a waiver of, or estoppel with respect to, such failure or any
subsequent or other failure. All remedies hereunder are cumulative and are not
exclusive of any other remedies provided by law.

        7.6    Entire Agreement.    This Agreement sets forth the entire
agreement and understanding of the parties relating to the subject matter
hereof, and supersedes all prior agreements and arrangements, written or oral,
relating to the subject matter hereof.

        7.7    Amendment.    This Agreement may be amended only by a written
instrument executed by both of the parties hereto.

        7.8    Successors and Assigns.    This Agreement shall inure to the
benefit of, and be binding upon, the parties hereto and their respective
successors. The Company may assign this Agreement without the prior consent of
Executive or his successors and assigns. Nothing in this Agreement, express or
implied, is intended to confer on any person other than the parties hereto and
the Released Parties, or their respective successors or permitted assigns, any
rights, remedies, obligations or liabilities under or by reason of this
Agreement.

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        7.9    Counterparts.    This Agreement may be executed in one or more
counterparts, each of which shall be deemed an original, but all of which
together shall constitute one and the same instrument.

        7.10    Remedies.    The parties hereto acknowledge and agree that money
damages may not be an adequate remedy for breach of any provision of this
Agreement and that any party hereto shall be entitled, in its sole discretion
and in addition to any other remedies it may have under this Agreement or
applicable law, to apply to any court of competent jurisdiction for specific
performance or injunctive relief in order to enforce or prevent any violations
of the provisions of this Agreement. All remedies, rights, undertakings,
obligations and agreements contained in this Agreement shall be cumulative and
none of them shall be in limitation of any other remedy, right, undertaking,
obligation or agreement of either party.

        7.11    Notice.    Any notice required or permitted by this Agreement
shall be in writing and shall be deemed delivered when delivered personally or
by overnight courier or sent by telegram, fax, or email, or forty-eight
(48) hours after being deposited in the U.S. mail, as certified or registered
mail, with postage prepaid, and addressed to the party to be notified at such
party's address or fax number set forth on the signature page hereto, which
address or fax number may be subsequently modified by a written notice delivered
in accordance with this section.

        7.12    Expenses.    Each party shall bear its own expenses arising out
of, or related to, the preparation and negotiation of this Agreement and the
transactions contemplated hereby.

        7.13    Attorneys Fees.    With respect to any action arising out of, or
related to this Agreement, the substantially prevailing party shall be entitled
to its reasonable attorneys' fees and costs.

        7.14    Opportunity to Consult with Legal Counsel.    Executive
acknowledges and agrees that he has had an opportunity to consult and review
this Agreement with independent legal counsel of his choosing, and that he fully
understands his rights and obligations hereunder.

        7.15    Jurisdiction; Consent to Service of Process.    

        (a)    Jurisdiction.    The parties hereto hereby irrevocably and
unconditionally submit to the jurisdiction of any Delaware State court or
federal court sitting in Delaware and any appellate court from any such court,
in any suit, action or proceeding arising out of or relating to this Agreement,
or for recognition or enforcement of any judgment resulting from any such suit,
action or proceeding, and each party hereby irrevocably and unconditionally
agrees that all claims in respect of any such suit, action or proceeding may be
heard and determined in such Delaware State court or, to the extent permitted by
law, by removal or otherwise, in such federal court. Each party hereto hereby
irrevocably and unconditionally waives, to the fullest extent legally possible,
(i) any objection which it may now or hereafter have to the laying of venue of
any suit, action or proceeding arising out of or relating to this Agreement in
any Delaware State court or any federal court sitting in Delaware, (ii) the
defense of an inconvenient forum to the maintenance of such suit, action or
proceeding in any such court and (iii) the right to object, with respect to such
suit, action or proceeding, that such court does not have jurisdiction over such
party.

        (b)    Consent to Service of Process.    Each party consents to the
service of copies of the summons and complaint and any other process which may
be served in any such action or proceeding by the mailing or delivering of a
copy of such process to such party at the address set forth on the signature
page hereto.

        7.16    Section Headings.    The section headings contained herein are
for reference purposes only, and shall not in any way affect the meaning or
interpretation of this Agreement.

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TAKE THIS RELEASE HOME, READ IT, AND CAREFULLY CONSIDER ALL OF ITS PROVISIONS
BEFORE SIGNING IT: IT INCLUDES A RELEASE OF KNOWN AND UNKNOWN CLAIMS. IF YOU
WISH, YOU SHOULD TAKE ADVANTAGE OF THE FULL CONSIDERATION PERIOD AFFORDED BY
SECTION 6.3 AND YOU SHOULD CONSULT YOUR ATTORNEY.

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        IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the    day of January, 2003.

NORTHWESTERN CORPORATION   MERLE D. LEWIS                     By:   /s/  GARY G.
DROOK      

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Name: Gary G. Drook
Title: Chief Executive Officer   /s/  MERLE D. LEWIS      

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              Address for Notice:
Attention Corporate Secretary
125 S. Dakota Avenue
Sioux Falls, SD 57104
fax: (605) 978-2817   Address for Notice:
3101 South Bishop
Sioux Falls, SD 57103
fax: (605) 338-1307

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Exhibit A

List of Plans

NorthWestern Corporation's Employee Stock Ownership Plan and Trust Agreement, as
amended and restated effective as of January 1, 2001

NorthWestern Corporation's Stock Option and Incentive Plan, as amended on
January 16, 2001

NorthWestern Team Member Stock Purchase Plan

NorthWestern Public Service Company Family Protector Benefit Plan, as amended
July 1, 1995

NorthWestern Corporation's Supplemental Income Security Plan, as amended and
restated effective July 1, 1999

NorthWestern Corporation 401(k) Retirement Savings Plan, as amended and restated
effective January 1, 2001

NorthWestern Corporation Supplemental Variable Investment Plan, as amended and
restated effective January 1, 2000

NorthWestern Corporation Dividend Reinvestment and Direct Stock Purchase Plan

10

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Exhibit B

Pension Plans

NorthWestern Pension Plan, as amended and restated effective as of January 1,
2000

NorthWestern Corporation Traditional Pension Equalization Plan, as amended and
restated effective as of January 1, 2000

11

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Exhibit C

Form of Press Release

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QuickLinks

Exhibit 10.1(i)

Recitals
Terms of Agreement