Exhibit
      4.1


Document
                  Number
              **THIRTY-EIGHTH**
                **SUPPLEMENTAL
                  INDENTURE**Recording
                  AreaName
                  and
                  Return Address
                
                Wisconsin
                  Public Service Corporation
                Attention:
                  Real Estate Department
                P.O.
                  Box
                  19001
                Green
                  Bay,
                  Wisconsin 54307-9001See
                  Schedule A
                  heretoParcel
                  Identification Number (PIN)








**THIRTY-EIGHTH**








**SUPPLEMENTAL
      INDENTURE**








**FROM**














**WISCONSIN
      PUBLIC SERVICE**


**CORPORATION**











**TO**














**U.S.
      BANK
      NATIONAL ASSOCIATION**


**(Successor
      to Firstar Bank National Association,**


**Successor
      to Firstar Trust Company,**


**Formerly
      Known as First Wisconsin Trust Company)**


**TRUSTEE**








**______________**








**DATED
      AS OF
      AUGUST 1, 2006**








**______________**








**SUPPLEMENTAL**


**To**


**First
      Mortgage and Deed of Trust**


**Dated
      as of
      January 1, 1941**


MI


WISCONSIN
      PUBLIC
      SERVICE CORPORATION


THIRTY-EIGHTH
      SUPPLEMENTAL INDENTURE





Dated
      as of August
      1, 2006





TABLE
      OF
      CONTENTS


____________










PAGEParties
            1Recitals
            1Form of Bond of Collateral Series F
            3Form of Trustee’s Certificate
            8Form of Prepayment Record
            8Further Recitals
            8ARTICLE I. FORM AND EXECUTION OF BONDS OF NEW
              SERIES
            9SECTION 1.01.  Certain Definitions
            9SECTION 1.02.  Terms of Bonds of New
              Series
            10SECTION 1.03.  Limitation of New Series
              to $22,000,000
            10SECTION 1.04.
            10(a) Redemption in Certain
              Extraordinary Events
            10(b) Redemption in Event of
              Default Under Section 9.01(e) of 2006 Village Indenture
            11(c) Redemption in Event of
              Taxability of Interest on Series 2006 Village Bonds
            11SECTION 1.05.  Notice of, and selection
              of Bonds of New Series for, Redemption
            12SECTION 1.06.  Redemption in Event of
              Default Under Section 6.01 of the Senior Indenture
            13SECTION 1.07.  Partial Redemption and
              Payments of Redemption Price Without Presentation of Bonds and New
              Series
            13SECTION 1.08.  Company Not Obligated to
              Make any Transfer of Bonds of New Series for Fifteen Days Before any
              Interest Payment Date
            13SECTION 1.09.  Charges for Transfer of
              Bonds of New Series
            13SECTION 1.10.  Bonds of New Series May
              Be Signed by Facsimile Signatures of Compay Officers
            14SECTION 1.11.  Payment Dates Falling on
              Saturday, Sunday or Legal Holiday
            14SECTION 1.12.  Bonds of New Series Redeemed or Paid
                Not Reissuable, but May Be Basis for Issuance of Bonds of
                Different Series, Credits or Cash Withdrawals.
            14ARTICLE II.  CONFIRMATION OF LIEN
            14SECTION 2.01.  Granting Clauses and
              Habendum
            14


i







ARTICLE
              III.  PARTICULAR COVENANTS OF THE COMPANY
            15SECTION 3.01.  Duly Authorized by Law to Execute and Deliver
              Supplemental Indenture and Issue Bonds
            15SECTION 3.02.  Covenant of Lawful Possession, Right to Mortgage
              Property and to Maintain Lien of Indenture
            15SECTION 3.03.
            15(a) Payment of Principal and Interest
            15(b) Payments and Credits
            15SECTION 3.04.  Nonliability of Trustee
            16ARTICLE
              IV.  MISCELLANEOUS
            16SECTION 4.01.  Recitals Not Made by Trustee.  No representations
                Made by Trustee.  Trust Accepted Subject to Terms
                andConditions
                of
                Indenture
            16SECTION 4.02.  Supplemental Indenture to be Construed as Part of
              Indenture
            16SECTION 4.03.
            17(a) References to Either Party to Supplemental Indenture Includes
              Successors or Assigns
            17(b) Table of Contents and Descriptive Headings of Articles Not to Affect
              Meaning
            17SECTION 4.04
            17(a) Trust Indenture Act Requirements Control
            17(b) Severability of Supplemental Indenture Provisions and Bond
              Provisions
            17SECTION 4.05.  Provisions for Execution in Counterparts
            17SECTION 4.06.  Supplemental Indenture Effective on Execution and
              Delivery
            17SECTION 4.07.  Names and Addresses of Debtor and Secured
              Party
            17





ii


**Thirty-
      Eighth Supplemental Indenture,** made as of the 1st
      day of August, 2006 by and between Wisconsin
      Public
      Service Corporation ,
      a corporation
      duly organized and existing under and by virtue of the laws of the State of
      Wisconsin, having its principal office in the City of Green Bay in said State
      (hereinafter sometimes called the “Company”), party of the first part, and U.S.
      Bank National Association (successor
      to
      Firstar Bank, National Association, successor to Firstar Trust Company, formerly
      known as First Wisconsin Trust Company), a national banking association duly
      organized and existing under and by virtue of the laws of the United States,
      having its Corporate Trust Services Office in the City of St. Paul in the State
      of Minnesota, as Trustee (hereinafter sometimes called the “Trustee”), party of
      the second part.




Whereas, the Company has
      heretofore executed and delivered to the predecessor of the Trustee its First
      Mortgage and Deed of Trust made as of January 1, 1941 (hereinafter
      referred to as the “1941 Mortgage”) and has heretofore executed and delivered to
      the predecessor of the Trustee supplemental indentures dated and hereinafter
      referred to as follows:




**Supplemental
                Indenture**
              **Dated
                (as of)**
            **Hereinafter
                referred to as**November
                1,
                1947
            First
                Supplemental Indenture*August
                1,
                1948
            Second
                Supplemental IndentureSeptember
                1,
                1949
            Third
                Supplemental IndentureNovember
                1,
                1950
            Fourth
                Supplemental Indenture*May
                1,
                1953
            Fifth
                Supplemental Indenture*January
                1,
                1954
            Sixth
                Supplemental IndentureOctober
                1,
                1954
            Seventh
                Supplemental IndentureDecember
                1,
                1957
            Eighth
                Supplemental IndentureNovember
                1,
                1959
            Ninth
                Supplemental IndentureOctober
                1,
                1963
            Tenth
                Supplemental IndentureJune
                1,
                1964
            Eleventh
                Supplemental IndentureNovember
                1,
                1967
            Twelfth
                Supplemental IndentureApril
                1,
                1969
            Thirteenth
                Supplemental IndentureAugust
                1,
                1970
            Fourteenth
                Supplemental IndentureMay
                1,
                1971
            Fifteenth
                Supplemental IndentureAugust
                1,
                1973
            Sixteenth
                Supplemental Indenture*September
                1,
                1973
            Seventeenth
                Supplemental IndentureOctober
                1,
                1975
            Eighteenth
                Supplemental IndentureFebruary
                1,
                1977
            Nineteenth
                Supplemental IndentureJuly
                15,
                1980
            Twentieth
                Supplemental IndentureDecember
                1,
                1980
            Twenty-First
                Supplemental Indenture*April
                1,
                1981
            Twenty-Second
                Supplemental IndentureFebruary
                1,
                1984
            Twenty-Third
                Supplemental IndentureMarch
                15,
                1984
            Twenty-Fourth
                Supplemental IndentureOctober
                1,
                1985
            Twenty-Fifth
                Supplemental IndentureDecember
                1,
                1987
            Twenty-Sixth
                Supplemental Indenture*September
                1,
                1991
            Twenty-Seventh
                Supplemental IndentureJuly
                1,
                1992
            Twenty-Eighth
                Supplemental Indenture





1


**Supplemental
                  Indenture**
                **Dated
                  (as of)**
              **Hereinafter
                referred to
                as**October
                  1, 1992
              Twenty-Ninth
                  Supplemental IndentureFebruary
                  1, 1993
              Thirtieth
                  Supplemental IndentureJuly
                  1, 1993
              Thirty-First
                  Supplemental IndentureNovember
                  1, 1993
              Thirty-Second
                  Supplemental IndentureDecember
                  1, 1998
              Thirty-Third
                  Supplemental IndentureAugust
                  1, 2001
              Thirty-Fourth
                  Supplemental IndentureDecember
                  1, 2002
              Thirty-Fifth
                  Supplemental IndentureDecember
                  1, 2003
              Thirty-Sixth
                  Supplemental IndentureDecember
                  1, 2006
              Thirty-Seventh
                  Supplemental
                  Indenture


_________________





* Includes
      amendments
      to or modifications of certain provisions of the 1941 Mortgage.





(said
      1941
      Mortgage, as supplemented, amended or modified by the aforesaid Supplemental
      Indentures, being hereinafter referred to as the “Indenture”, except as such
      term is differently defined and used in and for the purposes of the Form of
      Bond
      of Collateral Series F and the Form of Trustee’s Certificate hereinafter set
      forth), whereby the Company granted, bargained, sold, warranted, released,
      conveyed, assigned, transferred, mortgaged, pledged, set over and confirmed
      unto
      the Trustee, and to its respective successors in trust, upon the terms,
      conditions and trusts therein set forth, all the property as therein described,
      real, personal and mixed, then owned or thereafter acquired by the Company,
      with
      certain exceptions as in the granting clauses and definitions of the Indenture
      set forth, to be held by the Trustee in trust, under the terms and subject
      to
      the conditions of the Indenture, as security for the bonds of the Company issued
      and to be issued thereunder in accordance with the provisions of the Indenture;
      and




Whereas ,
      Section 2.01 of
      the 1941 Mortgage provides that bonds may be issued thereunder in one or more
      series, each series to have such distinctive designation as the Board of
      Directors of the Company may select for such series; and




Whereas ,
      the Company has
      heretofore issued and there are now outstanding, in accordance with the
      provisions of the 1941 Mortgage and said Supplemental Indentures bonds of
      several series designated “First Mortgage Bonds, 7-1/8% Series Due
      July 1, 2023”, “First Mortgage Bonds Due February 1, 2013”,
“First Mortgage Bonds Collateral Series A”, “First Mortgage Bonds
      Collateral Series B”, “First Mortgage Bonds Collateral Series C”, “First
      Mortgage Bonds Collateral Series D” and “First Mortgage Bonds Collateral Series
      E”; and




Whereas, the
      Company has agreed to issue $22,000,000 in aggregate principal amount of Senior
      Notes, Series Due February 1, 2013, (the “Related Securities”) pursuant to an
      Indenture, dated as of December 1, 1998, between the Company and a
      predecessor of U.S. Bank National Association, as trustee (the “Senior Trustee”)
      as supplemented; and




2


Whereas ,
      in order to
      secure the Company’s obligations to pay principal, premium, if any, and interest
      on the Related Securities, the Company is desirous of providing for the issuance
      under the Indenture of bonds of a new series designated as “First Mortgage
      Bonds, Collateral Series F”, in an aggregate principal amount of not more than
      $22,000,000, the bonds of said series to be issued as registered bonds without
      coupons in any denominations that the Company may from time to time execute
      and
      deliver, the bonds of said series, the Trustee’s Certificate, and the Form of
      Prepayment Record to be substantially in the tenor following:






(Form
      of Bond of
      Collateral Series F)




No._____________  $_____________





Wisconsin
      Public
      Service Corporation


(Incorporated
      under
      the laws of the State of Wisconsin)





First
      Mortgage
      Bond, Collateral Series F





THE
      FIRST MORTGAGE
      BONDS, COLLATERAL SERIES F (HEREINAFTER, “COLLATERAL BONDS”), REPRESENTED BY
      THIS CERTIFICATE ARE BEING ISSUED AND DELIVERED BY THE COMPANY TO U.S. BANK
      NATIONAL ASSOCIATION, AS TRUSTEE (IN SUCH CAPACITY, THE “SENIOR TRUSTEE”) UNDER
      AN INDENTURE, DATED AS OF DECEMBER 1, 1998, BETWEEN THE COMPANY AND A
      PREDECESSOR OF THE SENIOR TRUSTEE, AS PREVIOUSLY SUPPLEMENTED AND AS
      SUPPLEMENTED BY THE SIXTH SUPPLEMENTAL INDENTURE THERETO DATED AS OF DECEMBER
      1,
      2006 (AS SO SUPPLEMENTED, THE “SENIOR INDENTURE”). THE COLLATERAL BONDS ARE TO
      BE HELD IN TRUST AS COLLATERAL FOR THE BENEFIT OF THE HOLDERS OF $22,000,000
      AGGREGATE PRINCIPAL AMOUNT OF SENIOR NOTES, SERIES DUE FEBRUARY 1, 2013 (THE
      “RELATED SECURITIES”) ISSUED PURSUANT TO THE SENIOR INDENTURE.




THE
      COLLATERAL
      BONDS MAY NOT BE SOLD OR OTHERWISE TRANSFERRED (EXCEPT TO A SUCCESSOR SENIOR
      TRUSTEE) UNTIL THE EARLIER OF THE RELEASE DATE (AS DEFINED BELOW) OR THE PRIOR
      RETIREMENT OF THE RELATED SECURITIES THROUGH REDEMPTION, REPURCHASE OR
      OTHERWISE.




THE
      COMPANY SHALL
      MAKE PAYMENTS OF THE PRINCIPAL OF, AND PREMIUM, IF ANY, AND INTEREST ON, THE
      COLLATERAL BONDS, TO THE SENIOR TRUSTEE, WHICH PAYMENTS SHALL BE APPLIED BY
      THE
      SENIOR TRUSTEE TO THE SATISFACTION OF OBLIGATIONS ON THE RELATED
      SECURITIES.




THE
      MATURITY DATE
      SPECIFIED ABOVE IS ALSO THE MATURITY DATE OF THE RELATED
      SECURITIES.




Wisconsin
      Public
      Service Corporation ,
      a corporation
      organized and existing under the laws of the State of Wisconsin (hereinafter
      called the Company), for value received, hereby promises to pay to U.S. BANK
      NATIONAL ASSOCIATION, as trustee for the benefit of the holders of the Related
      Securities, or registered assigns (in such capacity, the “Senior




3


Trustee”),
      at the
      Corporate Trust Services Office of U.S. Bank National Association, in Milwaukee,
      Wisconsin on the 1st day of February, 2013, the sum of
      ____________________________ DOLLARS ($___________) in lawful money of the
      United States of America, and to pay interest thereon from August 1, 2006 (or
      from the most recent date to which interest has been paid or duly provided
      for)
      semi-annually on February 1 and August 1 in each year, commencing
      February 1, 2007, (i) at the rate of 0% per annum prior to December 14,
      2006 and (ii) at the rate of 3.95% per annum from and after December 14, 2006,
      until the principal hereof is paid or made available for payment and (to the
      extent that the payment of such interest shall be legally enforceable) at the
      same rate for the applicable period on any overdue principal and premium and
      on
      any overdue installment of interest. The principal and interest so payable
      on
      any February 1 or August 1 will be paid to the person or entity in whose
      name this bond is registered, at the address thereof as it appears on the
      Company’s books for registration and registration of transfer.




The
      Related
      Securities are issued in order to evidence and secure a loan made by the Village
      of Weston, Wisconsin (the “Village”), to the Company pursuant to a Loan
      Agreement, dated as of April 1, 1981 as amended from time to time, including
      a
      Third Amendment to Loan Agreement, dated as of December 1, 2006. In order to
      fund such loan, the Village has agreed to issue $22,000,000 in principal amount
      of its Pollution Control Refunding Revenue Bonds, Series 2006 (Wisconsin Public
      Service Corporation Projects) (“Series 2006 Village Bonds”) under and pursuant
      to the 2006 Village Indenture (as defined in the Supplemental Indenture). The
      Series 2006 Village Bonds are payable from payments made, or caused to be made,
      by the Company of principal of, premium, if any, and interest on the Related
      Securities. Upon certain terms and conditions, credits arising from purchase
      or
      redemption of the Series 2006 Village Bonds shall be applied against payment
      obligations in connection with the Related Securities and the bonds of this
      series and to the extent so applied shall satisfy a like amount otherwise due
      thereunder.




This
      bond shall not
      be valid or become obligatory for any purpose unless and until U.S. Bank
      National Association, (successor to First Wisconsin Trust Company), as Trustee
      under the Indenture, or its successors thereunder, shall have signed the
      certificate of authentication endorsed hereon.




This
      bond is one of
      a duly authorized issue of bonds of the Company, known as its First Mortgage
      Bonds, of the series and designation indicated on the face hereof, which issue
      of bonds consists, or may consist, of several series of varying denominations,
      dates and tenors, all issued and to be issued under and equally secured (except
      in so far as a sinking fund, or similar fund, established in accordance with
      the
      provisions of the Indenture, may afford additional security for the bonds of
      any
      specific series) by a First Mortgage and Deed of Trust (herein called the
“Indenture”) dated as of January 1, 1941, executed by the Company to
      First Wisconsin Trust Company (subsequently succeeded by U.S. Bank National
      Association, herein called the Trustee), as Trustee, to which Indenture and
      all
      instruments supplemental thereto reference is hereby made for a description
      of
      the property mortgaged and pledged, the nature and extent of the security,
      the
      rights of the holders of the bonds as to such security, and the terms and
      conditions upon which the bonds may be issued under the Indenture and any
      instruments supplemental thereto and are secured. The principal hereof may
      be
      declared or may become due on the conditions, in the manner and at the time
      set
      forth in the Indenture, upon the happening of




4


a
      completed default as in the Indenture provided. This bond is one of a series
      created by a Supplemental Indenture (herein called the “Supplemental Indenture”)
      dated as of August 1, 2006, between the Company and the Trustee, which is
      supplemental to the Indenture.




The
      Senior Trustee
      has agreed pursuant to the Senior Indenture to hold the bonds of this series
      as
      collateral for the benefit of the holders of the Related Securities under all
      circumstances and not to transfer (except to a successor trustee) such bonds
      until the earlier of the Release Date or the prior retirement of the Related
      Securities through redemption, repurchase or otherwise. “Release Date” means the
      date on which all First Mortgage Bonds of the Company issued and outstanding
      under the Indenture, other than the bonds of this series and other bonds pledged
      as security for Securities issued under the Senior Indenture (collectively
      “Collateral Bonds”), have been retired (at, before or after the maturity
      thereof) through payment, redemption or otherwise, provided that no default
      or
      event of default has occurred and is continuing under the Senior Indenture.
      On
      the Release Date, the Senior Trustee shall deliver to the Company for
      cancellation all Collateral Bonds, and the Company shall cause the Senior
      Trustee to provide notice to all holders of Related Securities of the occurrence
      of the Release Date. As a result, on the Release Date, the bonds of this series
      shall cease to secure the Related Securities. Following the Release Date, the
      Company shall cause the Indenture to be discharged, and the Company shall not
      issue any additional Collateral Bonds thereunder, and from and after the Release
      Date, the Company’s obligations in respect of the Collateral Bonds shall be
      satisfied and discharged.




With
      the consent of
      the Company and to the extent permitted by and as provided in the Indenture
      and/or any instruments supplemental thereto, the rights and obligations of
      the
      Company and/or of the holders of the bonds, and/or terms and provisions of
      the
      Indenture and/or of any instruments supplemental thereto may be modified or
      altered by consent of the holders of at least seventy percent (70%) in principal
      amount of the bonds then outstanding under the Indenture and any instruments
      supplemental thereto (excluding bonds challenged and disqualified from voting
      by
      reason of the interest of the Company or of certain related persons therein
      as
      provided in the Indenture); provided that no such modification or alteration
      shall permit the extension of the maturity of the principal of this bond or
      the
      reduction in the rate of interest hereon or any other modification in the terms
      of payment of such principal or interest or the taking of certain other action
      as more fully set forth in the Indenture without the consent of the holder
      hereof.




The
      Company and the
      Trustee may deem and treat the person in whose name this bond is registered
      as
      the absolute owner hereof for the purpose of receiving payment of or on account
      of the principal hereof and interest hereon and for all other purposes, and
      shall not be affected by any notice to the contrary.




In
      certain extraordinary events described in paragraph (b) of Section 1.04 of
      the
      Supplemental Indenture, the bonds of this series are subject to redemption
      within one year following such extraordinary event, in whole but not in part,
      at
      the option of the Company, in each case at a redemption price equal to the
      principal amount thereof, together with accrued interest to the redemption
      date.




The
      Company shall
      call for redemption all of the bonds of this series then outstanding, and shall
      on the redemption date therefor redeem the same at a price equal to
      100%




5


of
      the principal amount thereof, together with accrued interest to the redemption
      date, in the event that the Company is notified by the 2006 Village Indenture
      Trustee (as defined in the Supplemental Indenture) that (i) an event of
      default has occurred and is continuing under Section 9.01(e) of the 2006 Village
      Indenture, and (ii) the 2006 Village Indenture Trustee has declared the
      principal of all Series 2006 Village Bonds then outstanding immediately due
      and
      payable pursuant to Section 9.02 of the 2006 Village Indenture. The redemption
      date shall be the accelerated maturity date of the Series 2006 Village Bonds;
      provided, however, that such requirement of redemption shall be deemed to be
      waived if prior to the date fixed for such redemption of the bonds of this
      series, the acceleration of the Series 2006 Village Bonds is waived or
      annulled.




The
      Company shall
      call for redemption all (or part if, in the opinion of nationally recognized
      bond counsel, a corresponding partial redemption of the Series 2006 Village
      Bonds will preserve the exclusion from gross income for Federal income tax
      purposes of interest on the remaining Series 2006 Village Bonds) of the bonds
      of
      this series then outstanding, and shall on the redemption date therefor redeem
      the same at a price equal to 100% of the principal amount thereof, together
      with
      accrued interest thereon to the redemption date, in the event that it is finally
      determined by the Internal Revenue Service or a court of competent jurisdiction
      that, as a result of a failure by the Company to observe any covenant, agreement
      or representation in the 2006 Village Revenue Agreement (as defined in the
      Supplemental Indenture), the interest payable on the Series 2006 Village Bonds
      is includable for Federal income tax purposes in the gross income of any owner
      of a Series 2006 Village Bond (other than an owner who is a “substantial user”
or a “related person” within the meaning of Section 103(b)(13) of the 1954 Code
      (as defined in the Supplemental Indenture) and the applicable regulations
      thereunder). Any such determination shall not be considered final for this
      purpose unless the Company has been given notice thereof, and if it so desires,
      has been afforded the opportunity, at its expense, to contest the same, either
      directly or in the name of any owner of Series 2006 Village Bonds, and until
      the
      conclusion of any appellate review, if sought. The redemption date shall be
      the
      120 th day after the date
      such determination becomes final or on such earlier date as the Company may
      designate.




Notice
      of any such
      redemption shall be hand delivered or mailed, by or on behalf of the Company,
      not less than thirty (30) days prior to the redemption date to the registered
      owner of the bonds so to be redeemed, at its address as the same shall appear
      on
      the Company’s books for registration and registration of transfer, all subject
      to the conditions and as more fully set forth in the Indenture and in the
      Supplemental Indenture, except that no newspaper publication shall be
      required.




In
      the event that an event of default under Section 6.01 of the Senior Indenture
      has occurred and is continuing, and the Senior Trustee has declared the
      principal of all of the Related Securities then outstanding immediately due
      and
      payable (or such principal has become ipso facto immediately due and payable)
      under Section 6.02 of the Senior Indenture, then the Company shall call for
      redemption and redeem all of the bonds of this series then outstanding at a
      price equal to 100% of the principal amount thereof, together with accrued
      interest thereon to the redemption date; provided that the Company may avail
      itself of the credits described in Section 3.03(b) of the Supplemental
      Indenture. The redemption date shall be the accelerated




6


maturity
      date of
      the Related Securities, and no prior notice of such redemption to the Trustee
      or
      the Senior Trustee shall be required.




This
      bond is
      nontransferable except to the Senior Trustee and successor trustees thereto.
      To
      the extent that it is transferable, it is transferable by the registered owner
      hereof in person or by attorney duly authorized in writing, on books of the
      Company to be kept for that purpose at the corporate trust services office
      of
      the Trustee at Milwaukee, Wisconsin, upon surrender hereof for cancellation
      at
      said office and upon presentation of a written instrument of transfer duly
      executed. Thereupon the Company shall issue in the name of the transferee,
      and
      the Trustee shall authenticate and deliver, a new registered bond or bonds
      without coupons of the same maturity and interest rate and of equal aggregate
      principal amount. Any such transfer shall be subject to the terms and conditions
      specified in the Indenture and the Supplemental Indenture.




No
      recourse shall be had for the payment of principal of, premium, if any, or
      interest on this bond, or any part thereof, or of any claim based hereon or
      in
      respect hereof or of the Indenture or any instrument supplemental thereto,
      against any incorporator, or any past, present or future stockholder, officer
      or
      director of the Company or of any predecessor or successor corporation, either
      directly or through the Company, or through any such predecessor or successor
      corporation, or through any receiver or a trustee in bankruptcy, whether by
      virtue of any constitution, statute or rule of law or by the enforcement of
      any
      assessment or penalty or otherwise, all such liability being, by the acceptance
      hereof and as a part of the consideration for the issue hereof, expressly waived
      and released, as more fully provided in the Indenture.




In
      Witness Whereof, Wisconsin Public Service Corporation has caused this
      bond to be signed in its name by the manual or facsimile signature of its
      President or a Vice President and its corporate seal or a facsimile thereof
      to
      be hereto affixed and attested by the manual or facsimile signature of its
      Secretary or an Assistant Secretary.




Dated
      as
      of:





Wisconsin
      Public
      Service Corporation,











By:____________________________


______
      President


Attest:





_____________________________


Secretary


7




(Form
      of Trustee’s
      Certificate)




This
      bond is one of
      the bonds of the series designated therein, described in the within mentioned
      Indenture and Supplemental Indenture.










U.S.
      Bank National
      Association,


As
      Trustee








By:________________________


Authorized
      Signature









(Form
      of Prepayment
      Record)




PREPAYMENT
      RECORD





Principal
      Amount Of
      Bond **$__________**





Date
      of maturity:
      February 1, 2013





**Prepayments
                on Principal****Amount**
            **Date**
            **Balance**
              **Outstanding**
            **Signature
                of Authorized**
              **Officer
                and Title**





and




Whereas ,
      the 1941 Mortgage
      provides that the Company and the Trustee may enter into indentures supplemental
      thereto for the purposes, among others, of providing the terms and conditions
      of
      the issue of the bonds of any new series; and




Whereas ,
      the Company is
      presently engaged within the States of Wisconsin and Michigan in conveying,
      distributing, supplying and serving electricity and gas and intends that this
      Supplemental Indenture shall be received for record and for filing in the
      appropriate public offices of said States or of any other jurisdiction in which
      there may be located from time to time properties intended to be subject to
      the
      lien of the Indenture in the manner and with the effect provided by their
      respective laws in respect to mortgages by, and security interests in existing
      and hereafter acquired properties of, a corporation so engaged; and




Whereas ,
      the execution and
      delivery of this Supplemental Indenture and the issue of bonds as in this
      Supplemental Indenture and the Indenture provided have been duly authorized
      by a
      resolution adopted by the Board of Directors of the Company; and




8


Whereas ,
      all things
      necessary to make the bonds of Collateral Series F, when duly issued and
      executed by the Company, and authenticated and delivered by the Trustee, valid,
      binding and legal obligations of the Company, and to make the Indenture and
      this
      Supplemental Indenture valid, binding and legal instruments for the security
      thereof, have been done and performed and the issue of said bonds, as in this
      Supplemental Indenture and the Indenture provided, has been in all respects
      duly
      authorized;




Now,
      Therefore,
      This Supplemental Indenture Witnesseth: Wisconsin
      Public
      Service Corporation, in consideration of the premises and of one dollar to
      it
      duly paid by the Trustee at or before the ensealing and delivery of these
      presents, the receipt whereof is hereby acknowledged, does hereby covenant
      and
      agree to and with U.S. Bank National Association, as Trustee, as
      follows:






ARTICLE
      I.




Form
      And Execution
      Of Bonds Of New Series




SECTION
      1.01.  Certain
      Definitions.  The
      following terms
      shall, for all purposes of this Supplemental Indenture, have the following
      meanings unless the context otherwise requires:




The
      term “1954
      Code” means the Internal Revenue Code of 1954 as in effect immediately prior to
      the effective date of the Tax Reform Act of 1986.




The
      term “Projects”
means those of the facilities described in Exhibit A to the Third Amendment
      to
      Loan Agreement which are refinanced with the Series 2006 Village
      Bonds.




The
      term “Third
      Amendment to Loan Agreement” means the Third Amendment to Loan Agreement, dated
      as of December 1, 2006, between the Village and the Company.




The
      term “Village”
means the Village of Weston, a municipal corporation and political subdivision
      duly organized and existing under the laws of the State of Wisconsin (and which
      is successor to the Town of Weston), located within the County of Marathon
      of
      the State of Wisconsin.




The
      term “Series
      2006 Village Bonds” means the Village of Weston, Wisconsin Pollution Control
      Refunding Revenue Bonds, Series 2006 (Wisconsin Public Service Corporation
      Projects), to be authenticated and delivered under and pursuant to the 2006
      Village Indenture in the principal amount of $22,000,000.




The
      term “2006
      Village Indenture” means the Indenture of Trust, dated as of December 1, 2006,
      between the Village and U.S. Bank National Association, as 2006 Village
      Indenture Trustee.




The
      term “2006
      Village Indenture Trustee” means the person, corporation or banking association
      acting as trustee from time to time under the 2006 Village
      Indenture.




9


The
      term “2006
      Village Revenue Agreement” means the Loan Agreement, dated as of April 1, 1981,
      between the Village and the Company, as previously amended and as amended by
      the
      Third Amendment to Loan Agreement.




SECTION
      1.02.  Terms
      of Bonds of
      New Series.  There
      is hereby
      created, for issuance under the Indenture on the date of authentication and
      delivery of the Related Securities, a series of bonds designated as Collateral
      Series F (herein sometimes referred to as the bonds of Collateral Series F),
      each of which shall bear the descriptive title “First Mortgage Bond, Collateral
      Series F”. The bonds of said series shall be issued only in the form of
      registered bonds without coupons and shall be substantially of the tenor and
      purport, and in the form, hereinbefore recited. The bonds of said series shall
      mature on February 1, 2013, and shall be issued in any denominations that the
      Company may execute and deliver. The bonds of said series shall bear interest
      at
      the rate of 0% per annum prior to December 14, 2006, and at the rate of 3.95%
      per annum from and after December 14, 2006, **** and
      such interest
      shall accrue from August 1, 2006 (or from the most recent date to which
      interest on the bonds of said series has been paid or provided for). Bonds
      of
      said series issued prior to February 1, 2007 shall be dated as of August 1,
      2006, and bonds of said series issued on and after February 1, 2007 shall be
      dated as provided in Section 2.09 of the 1941 Mortgage. Principal and interest
      will be payable to the registered owner of the bonds of said series, and at
      the
      address thereof, appearing on the Company’s books for registration and
      registration of transfer. Said bonds will be nontransferable except to the
      Senior Trustee and successors thereto, if any.




SECTION
      1.03.  Limitation
      of New
      Series to $22,000,000.  The
      aggregate
      principal amount of all bonds of Collateral Series F which may at any time
      be
      certified, issued and outstanding shall be limited to $22,000,000, and bonds
      of
      said series may be executed, authenticated, delivered and issued hereunder
      from
      time to time subject to the restrictions and provisions contained in this
      Supplemental Indenture and in the 1941 Mortgage.




SECTION
      1.04.




(a)  Redemption
      in
      Certain Extraordinary Events.  The
      bonds of
      Collateral Series F shall also be subject to redemption at any time at the
      option and direction of the Company, as a whole and not in part, at a redemption
      price equal to 100% of the principal amount thereof, together with accrued
      interest to the redemption date, if any one or more of the following events
      shall have occurred:




(i)  Unit
      3 (“Unit 3”)
      at the Company’s coal-fired power plant located in Marathon County, Wisconsin
      and known as the Weston Power Plant shall have been damaged or destroyed to
      such
      an extent that, in the opinion of the Board of Directors of the Company, it
      cannot reasonably be restored within six months to the condition thereof
      immediately preceding such damage or destruction;




(ii)  Unit
      3 shall have
      been damaged or destroyed to such an extent that normal operation of Unit 3
      is
      thereby prevented for a period of at least six months;




(iii)  title
      to, or
      temporary use of, all or substantially all of Unit 3 shall have been taken
      under
      the power of eminent domain or sold under the threat of such






10




taking,
      or there
      shall be a taking of any part of the Projects or other property interest of
      the
      Company in connection with which Unit 3 is used as results or is likely to
      result in the inability to carry on normal operation of Unit 3 for a period
      of
      at least six months;




(iv)  the
      2006 Village
      Revenue Agreement shall become void or unenforceable or impossible of
      performance in accordance with the intent and purpose of the parties as
      expressed therein, or unreasonable burdens or excessive liabilities related
      to
      the 2006 Village Revenue Agreement or the Projects shall be imposed on the
      Village or the Company as a result of any change in the Constitution of the
      State of Wisconsin or the Constitution of the United States of America or as
      a
      result of any legislative, administrative or judicial action;




(v)  a
      final order or
      decree of any court or administrative body shall require that a substantial
      part
      of the operations at Unit 3 cease or be terminated to such extent that normal
      operation of Unit 3 will be, or is likely to be, prevented for a period of
      at
      least six months;




(vi)  changes,
      which the
      Company cannot reasonably control, in the economic availability of materials,
      fuel, supplies, labor, equipment or other properties or things necessary for
      the
      efficient operation of Unit 3 shall have occurred which, in the judgment of
      the
      Board of Directors of the Company, render the continued operation of Unit 3
      uneconomic; or




(vii)  changes
      in
      circumstances, including, but not limited to, changes in pollution control
      requirements, shall have occurred such that the Board of Directors of the
      Company shall determine that use of the Projects is no longer required or
      desirable.




Any
      such redemption
      shall be on a date which is within one year following the occurrence of one
      of
      the events listed above permitting the exercise of the option.





(b)  Redemption
      in Event
      of Default Under Section 9.01(e) of 2006 Village Indenture.  The
      Company shall
      call for redemption of all of the bonds of Collateral Series F then outstanding,
      and shall on the redemption date therefor redeem the same at a price equal
      to
      100% of the principal amount thereof, together with accrued interest to the
      redemption date, in the event that the Company is notified by the 2006 Village
      Indenture Trustee that (i) an event of default has occurred and is
      continuing under Section 9.01(e) of the 2006 Village Indenture, and
      (ii) the 2006 Village Indenture Trustee has declared the principal of all
      Series 2006 Village Bonds then outstanding immediately due and payable pursuant
      to Section 9.02 of the 2006 Village Indenture. The redemption date shall be
      the
      accelerated maturity date of the Series 2006 Village Bonds; provided, however,
      that such requirement of redemption shall be deemed to be waived if prior to
      the
      date fixed for such redemption of the bonds of Collateral Series F, the
      acceleration of the Series 2006 Village Bonds is waived or annulled.




(c)  Redemption
      in Event
      of Taxability of Interest on Series 2006 Village Bonds.  The
      Company shall
      call for redemption all (or part if, in the opinion of nationally recognized
      bond counsel, a corresponding partial redemption of the Series 2006 Village
      Bonds will
      preserve the
      exclusion from gross income for Federal income tax purposes of interest on
      the




11




remaining
      Series
      2006 Village Bonds) of the bonds of Collateral Series F then outstanding, and
      shall on the redemption date therefor redeem the same at a price equal to 100%
      of the principal amount thereof, together with accrued interest thereon to
      the
      redemption date, in the event that it is finally determined by the Internal
      Revenue Service or a court of competent jurisdiction that, as a result of a
      failure by the Company to observe any covenant, agreement or representation
      in
      the 2006 Village Revenue Agreement, the interest payable on the Series 2006
      Village Bonds is includable for Federal income tax purposes in the gross income
      of any owner of a Series 2006 Village Bond (other than an owner who is a
“substantial user” or a “related person” within the meaning of Section
      103(b)(13) of the 1954 Code and the applicable regulations thereunder). Any
      such
      determination shall not be considered final for this purpose unless the Company
      has been given notice thereof, and if it so desires, has been afforded the
      opportunity, at its expense, to contest the same, either directly or in the
      name
      of any owner of Series 2006 Village Bonds, and until the conclusion of any
      appellate review, if sought. The redemption date shall be the 120 th day after the date
      such determination becomes final or on such earlier date as the Company may
      designate.




SECTION
      1.05.  Notice
      of, and
      selection of Bonds of New Series for, Redemption.  In
      the event that
      the Company shall desire to exercise its right, or is required by the provisions
      of Section 1.04 of this Supplemental Indenture, to redeem and pay all or any
      part of the bonds of Collateral Series F, it shall, except as modified herein,
      comply with the terms and conditions of Article XI of the Indenture with regard
      to the redemption of bonds of any series secured thereby, and such redemption
      shall be made under and subject to the terms and provisions of said Article
      XI
      and in the manner and with the effect stated therein; provided, however, (a)
      the
      Company shall specify, in accordance with the provisions of this Supplemental
      Indenture, those bonds of Collateral Series F which are to be redeemed if only
      a
      part thereof are to be redeemed, and payments in redemption of bonds of
      Collateral Series F shall be made directly by the Company to the registered
      owners of the bonds entitled thereto; (b) the Company may avail itself of the
      credits described in Section 3.03(b) hereof; and (c) the provisions of Section
      11.03(b) of the 1941 Mortgage shall not be applicable to any such redemption.
      The Company shall not exercise any option to redeem on any date all or any
      part
      of the bonds of Collateral Series F unless it shall give a valid direction
      under
      the Senior Indenture for the redemption on such date of an equal amount of
      Related Securities. Notice of each such redemption shall be hand delivered
      or
      mailed, by certified mail, with return receipt requested, by or on behalf of
      the
      Company, at least thirty (30) days prior to the redemption date, to the
      registered owner of the bonds which are to be redeemed at its address appearing
      on the Company’s books for registration and registration of transfer. Such
      delivery or mailing (but not the receipt thereof or the return of the receipt
      so
      requested) shall be a condition to the redemption of the bonds. All bonds so
      redeemed shall forthwith be delivered to the Trustee and cancelled, but only
      when the principal, premium, if any, and accrued interest thereon is paid in
      full. The Trustee, when required to select bonds of Collateral Series F for
      redemption, shall promptly notify the Company, and the Company, when selecting
      bonds of Collateral Series F for redemption, shall promptly notify the Trustee,
      in writing of the distinctive numbers of the bonds selected for redemption
      in
      whole or in part. For the purpose only of complying with the Indenture
      (particularly Section 11.02 thereof) in connection with the redemption of bonds
      of Collateral Series F, for each $5,000 principal amount of bonds authenticated
      and delivered hereunder
      there
      shall be assigned a number in such manner and at such time as the Trustee or
      the
      Company shall deem appropriate.






12




SECTION
      1.06.  Redemption
      in Event
      of Default Under Section 6.01 of the Senior Indenture.  The
      Company shall
      call for redemption all of the bonds of Collateral Series F then outstanding,
      and shall on the redemption date therefor redeem the same at a price equal
      to
      100% of the principal amount thereof, together with accrued interest to the
      redemption date, in the event that an event of default has occurred and is
      continuing under Section 6.01 of the Senior Indenture, and the Senior Trustee
      has declared the principal of all Related Securities then outstanding
      immediately due and payable (or such principal has become ipso facto immediately
      due and payable) pursuant to Section 6.02 of the Senior Indenture; provided
      that, in such event, the Company may avail itself of the credits described
      in
      Section 3.03(b) hereof. The redemption date shall be the accelerated maturity
      date of the Related Securities; provided, however, that such requirement of
      redemption shall be deemed to be waived if prior to the date fixed for such
      redemption of the bonds of Collateral Series F, the acceleration of the Related
      Securities is waived or annulled. Any provision of Article XI of the
      Indenture notwithstanding, no prior notice of such redemption of the bonds
      of
      Collateral Series F to the Trustee or the Senior Trustee shall be
      required.




SECTION
      1.07.  Partial
      Redemption
      and Payments of Redemption Price Without Presentation of Bonds and New
      Series.  Subject
      to the
      provisions of Sections 1.04 and 1.05 of this Supplemental Indenture, Bonds
      of
      Collateral Series F may be redeemed in part, but the portion of any such bond
      so
      redeemed in part shall be Five Thousand Dollars ($5,000) or an integral multiple
      thereof. In case any bond shall be redeemed in part only, payment of the
      redemption price of such portion of the bond of Collateral Series F shall be
      made by the Company (or Trustee, as the case may be) to the registered owner
      thereof, at its address appearing on the Company’s books for registration and
      registration of transfer of bonds of Collateral Series F without presentation
      or
      surrender thereof, provided there is on file with the Company and Trustee (and
      not theretofore rescinded by written notice from such registered owner to the
      Company and Trustee) a written commitment from such registered owner to the
      effect that (1) payments will be so made, and (2) such registered owner will
      make notations on such bond or a paper attached thereto of the portion thereof
      so redeemed. Prior to any transfer by the registered owner of any bond of
      Collateral Series F, the same shall be surrendered to the Company or Trustee
      for
      appropriate notation thereon of, or in exchange for a new bond or bonds for,
      the
      unredeemed balance of the principal amount thereof. The Trustee shall not be
      under any duty to determine that any of the notations mentioned herein have
      been
      made or be liable in any manner with respect thereto.




SECTION
      1.08.  Company
      Not
      Obligated to Make any Transfer of Bonds of New Series for Fifteen Days Before
      any Interest Payment Date.  The
      Company shall
      not be obligated to make any transfer of bonds of Collateral Series F for a
      period of fifteen (15) calendar days next preceding any interest payment date,
      or next preceding any selection by lot of bonds to be redeemed. The Company
      shall not be obligated to make transfers of any bonds called or being called
      for
      redemption.




SECTION
      1.09.  Charges
      for
      Transfer of Bonds of New Series.  No
      charge shall be
      made to any registered owner of any bond of Collateral Series F for any transfer
      of bonds
      of said
      series except for any tax or other governmental charge required to be paid
      in
      connection therewith.






13




SECTION
      1.10.  Bonds
      of New Series
      May Be Signed by Facsimile Signatures of Company Officers.  The
      signatures of
      the President or a Vice President and of the Secretary or an Assistant Secretary
      upon the bonds of Collateral Series F may be facsimile signatures imprinted
      or
      otherwise reproduced on such bonds. Any such facsimile signature shall have
      the
      same effect and shall be subject to the same provisions set forth in Section
      2.13 of the 1941 Mortgage as to signatures upon bonds generally.




SECTION
      1.11.  Payment
      Dates
      Falling on Saturday, Sunday or Legal Holiday.  In
      the event that
      an interest payment or maturity date or a date fixed for redemption of any
      bond
      of Collateral Series F shall be a Saturday, Sunday or a legal holiday or a
      day
      on which banking institutions in the city of location of the registered address
      of the owner are authorized by law to close, then payment of interest or
      principal (and premium, if any) need not be made on such date, but may be made
      on the next succeeding business day not a Saturday, Sunday or a legal holiday
      or
      a day upon which banking institutions in the city of location of the registered
      address of the owner are authorized by law to close, with the same force and
      effect as if made on the date of maturity, interest date, or the date fixed
      for
      redemption, and no interest shall accrue for the period after such
      date.




SECTION
      1.12.  Bonds
      of New Series
      Redeemed or Paid Not Reissuable, but May Be Basis for Issuance of Bonds of
      Different Series, Credits or Cash Withdrawals.  Bonds
      of Collateral
      Series F which have been redeemed or have been paid at maturity shall not be
      reissued as bonds of said series, but may be made the basis for the issuance
      of
      additional bonds of any series hereafter created, or credits may be taken or
      cash withdrawn on the basis thereof under any applicable provisions of the
      1941
      Mortgage or any future supplemental indenture.




ARTICLE
      II.




Confirmation
      of
      Lien




SECTION
      2.01.  Granting
      Clauses
      and Habendum.  The
      Company, in
      order to record the description of, and confirm unto the Trustee, certain
      property acquired after the execution and delivery of the 1941 Mortgage and
      now
      subject to the lien thereof by virtue of the provisions of the 1941 Mortgage
      conveying to the Trustee property acquired after its execution and delivery,
      by
      these presents does grant, bargain, sell, warrant, release, convey, assign,
      transfer, mortgage, pledge, set over and confirm unto U.S. Bank National
      Association, as Trustee, and to its respective successors in said trust forever,
      subject to the rights reserved by the Company in and by other provisions of
      the
      Indenture and this Supplemental Indenture, all of the property described and
      mentioned or enumerated or referred to in a schedule hereto annexed and marked
      Schedule A, reference to said schedule for a description and enumeration of
      the property therein described and enumerated being hereby made with the same
      force and effect as if the same were incorporated herein at length;




Together
      with all
      and singular the tenements, hereditaments and appurtenances belonging or in
      any
      wise appertaining to the aforesaid property or any part thereof with the reversion
      and
      reversions, remainder and remainders, tolls, rents and revenues, issues, income,
      product and profits thereof, and all the estate, right, title and interest
      and
      claim whatsoever, at




14




law
      as well as in
      equity, which the Company now has or may hereafter acquire in and to the
      aforesaid property and every part and parcel thereof;




To
      have and to hold all said properties, mortgaged, pledged or conveyed by the
      Company as aforesaid, or intended so to be, unto the Trustee and its successors
      and assigns forever, subject, however, to permissible encumbrances as defined
      in
      the 1941 Mortgage; but in trust, nevertheless, for the same purposes and upon
      the same conditions as are fully set forth in the Indenture, which is hereby
      referred to.






ARTICLE
      III.




Particular
      Covenants Of The Company




In
      addition to the covenants contained in the Indenture, the Company hereby
      covenants as follows:




SECTION
      3.01.  Duly
      Authorized by
      Law to Execute and Deliver Supplemental Indenture and Issue Bonds.  That
      it is duly
      authorized under the laws of the State of Wisconsin and under all other
      applicable provisions of law to create and issue the bonds of Collateral Series
      F, and to execute and deliver this Supplemental Indenture, and that all
      corporate action on its part for the creation and issue of said bonds and the
      execution of this Supplemental Indenture has been duly and effectually taken,
      and that said bonds when issued and delivered to the owners thereof are and
      will
      be valid and enforceable obligations of the Company, and that the Indenture
      is
      and always will be a valid mortgage and deed of trust to secure the payment
      of
      said bonds.




SECTION
      3.02.  Covenant
      of Lawful
      Possession, Right to Mortgage Property and to Maintain Lien of
      Indenture.  That
      it is lawfully
      possessed of all the property mortgaged and pledged by the Indenture; that
      it
      will maintain and preserve the lien of the Indenture on the property mortgaged
      and pledged thereby in accordance with the terms thereof and hereof so long
      as
      any of the bonds issued thereunder are outstanding; and that it has good right
      and lawful authority to mortgage and pledge the property mortgaged and pledged
      thereby as provided in and by the Indenture; and that the same is free and
      clear
      of all liens and encumbrances, except permissible encumbrances as defined in
      the
      Indenture.




SECTION
      3.03.




(a)  Payment
      of
      Principal and Interest.  That
      the Company
      will duly and punctually pay to the registered owner of bonds of Collateral
      Series F issued under and secured by the Indenture and this Supplemental
      Indenture the principal and interest of said bonds at the dates and place and
      in
      the manner mentioned in such bonds.




(b)  Payments
      and
      Credits.  Provided,
      however:




Payments
      of the
      principal of, premium, if any, and interest on the bonds of the Collateral
      Series F may be made with moneys in the Bond Fund created under the 2006 Village
      Indenture, as provided in the 2006 Village Revenue Agreement and




15




the
      2006 Village
      Indenture. Money in said Bond Fund or earnings on investments which have been
      set aside by the 2006 Village Indenture Trustee at the request of the Company
      for payment of the principal of (whether at maturity or upon redemption),
      premium, if any, or interest on any Series 2006 Village Bonds shall be credited
      against the obligation of the Company to pay the principal of, premium, if
      any,
      or interest on bonds of the Collateral Series F. The principal amount of any
      Series 2006 Village Bond or Bonds acquired by the Company and delivered to
      the
      2006 Village Indenture Trustee for cancellation, or acquired by the 2006 Village
      Indenture Trustee and canceled, shall be credited against the obligation of
      the
      Company to pay the principal of the bonds of the Collateral Series
      F.




As
      the principal of, premium, if any, and interest on the bonds of the Collateral
      Series F are thereby paid or deemed paid in full, and upon their receipt by
      the
      Company, such bonds shall be delivered to the Trustee for cancellation. The
      Company shall promptly inform the Trustee of all payments made and credits
      availed of with respect to its obligations on bonds of the Collateral Series
      F.
      The Trustee shall not be required to recognize any payment made or credit
      availed of with respect to any bonds of the Collateral Series F unless it has
      received (a) the bond for cancellation by it, or (b) a certificate of the 2006
      Village Indenture Trustee specifying the amount of such payment or credit and
      the number of the bonds of the Collateral Series F with respect to which the
      payment or credit was applied. In the absence of receipt by the Trustee of
      the
      bond, any such certificate shall be controlling and conclusive.




SECTION
      3.04.  Nonliability
      of
      Trustee.  That
      the Trustee
      shall not incur any liability by reason of any default, failure or delay on
      the
      part of the Company to observe or perform its covenants contained in this
      Article III.






ARTICLE
      IV.




Miscellaneous




SECTION
      4.01.  Recitals
      Not Made
      by Trustee. No Representations Made by Trustee. Trust Accepted Subject to Terms
      and Conditions of Indenture.  The
      recitals of
      fact herein and in the bonds hereby created contained (except the Trustee’s
      Certificate) shall be taken as statements of the Company and shall not be
      construed as made or warranted by the Trustee. The Trustee makes no
      representations as to the validity of this Supplemental Indenture or of the
      bonds issued under the Indenture by virtue hereof. Except as herein otherwise
      provided, no duties, responsibilities or liabilities are assumed, or shall
      be
      construed to be assumed, by the Trustee by reason of this Supplemental Indenture
      other than as set forth in the Indenture; and this Supplemental Indenture is
      executed and accepted on behalf of the Trustee, subject to all the terms and
      conditions set forth in the Indenture, as fully to all intents as if the same
      were herein set forth at length.




SECTION
      4.02.  Supplemental
      Indenture to be Construed as Part of Indenture.  This
      Supplemental
      Indenture shall be construed in connection with and as a part of the
      Indenture.




16


SECTION
      4.03.




(a)   References
      to
      Either Party to Supplemental Indenture Includes Successors or
      Assigns.  Whenever
      in this
      Supplemental Indenture either of the parties hereto is named or referred to,
      such reference shall be deemed to include the successors or assigns of such
      party, and all the covenants and agreements in this Supplemental Indenture
      contained by or on behalf of the Company or by or on behalf of the Trustee
      shall
      bind and inure to the benefit of the respective successors and assigns of such
      parties, whether so expressed or not.




(b)  Table
      of Contents
      and Descriptive Headings of Articles Not to Affect Meaning.  The
      table of
      contents and the descriptive headings of the several Articles of this
      Supplemental Indenture were formulated, used and inserted in this Supplemental
      Indenture for convenience only and shall not be deemed to affect the meaning
      or
      construction of any of the provisions hereof.




SECTION
      4.04.




(a)  Trust
      Indenture Act
      Requirements Control.  If
      any provision of
      this Supplemental Indenture limits, qualifies, or conflicts with another
      provision of this Supplemental Indenture or of the Indenture required or deemed
      to be included in indentures qualified under the Trust Indenture Act of 1939
      (as
      enacted prior to the date of this Supplemental Indenture) by any of Sections
      310
      to 317, inclusive, of the said Act, such required provisions shall
      control.




(b)  Severability
      of
      Supplemental Indenture Provisions and Bond Provisions.  In
      case any one or
      more of the provisions contained in this Supplemental Indenture or in the bonds,
      issued hereunder and under the Indenture should be invalid, illegal, or
      unenforceable in any respect, the validity, legality and enforceability of
      the
      remaining provisions contained herein and therein shall not in any way be
      affected, impaired, prejudiced or disturbed thereby.





SECTION
      4.05.  Provisions
      for
      Execution in Counterparts.  This
      Supplemental
      Indenture may be executed in several counterparts, and all said counterparts
      executed and delivered, each as an original, shall constitute but one and the
      same instrument.




SECTION
      4.06.  Supplemental
      Indenture Effective on Execution and Delivery.  This
      Supplemental
      Indenture shall be effective and binding from and after the time of actual
      execution and delivery thereof, notwithstanding the fact that such execution
      and
      delivery may occur prior or subsequent to August 1, 2006.




SECTION
      4.07.  Names
      and Addresses
      of Debtor and Secured Party.  The
      debtor and its
      mailing address is WISCONSIN PUBLIC SERVICE CORPORATION, 700 North Adams Street,
      P.O. Box 19001, Green Bay, WI 54307. The secured party and its address, from
      which information concerning the security interest hereunder may be obtained,
      is
      U.S. BANK NATIONAL ASSOCIATION, Corporate Trust Services, 1555
      RiverCenter
      Drive, Suite 301, Milwaukee, WI 53212.




17


In
      Witness Whereof ,
      the party of the
      first part has caused its corporate name and seal to be hereunto affixed and
      this Supplemental Indenture to be signed by its President or Vice President,
      and
      attested by its Secretary or an Assistant Secretary, for and in its behalf,
      and
      the party of the second part has caused its corporate name to be hereunto
      affixed, and this Supplemental Indenture to be signed by its Vice President
      for
      and in its behalf, all done as of the first day of August, 2006.




Wisconsin
      Public
      Service Corporation,








By:
/s/
      Joseph P.
      O'Leary


(SEAL)       Joseph
      P.
      O’Leary


Senior
      Vice
      President and Chief


Financial
      Officer


Attest:








/s/
      Barth J. Wolf


Barth
      J.
      Wolf


Secretary





Executed
      by
      Wisconsin Public Service


Corporation,
      in
      presence of:





/s/ Mark Van De
      Laarschot


Mark
      Van De
      Laarschot





/s/ Patti L. Herrmann


Patti
      L.
      Herrmann





U.S.
      Bank National
      Association,


As
      Trustee,








By:
/s/
      Peter M.
      Brennan


Peter
      M.
      Brennan


Vice
      President





Executed
      by U.S.
      Bank National Association


in
      presence of:





/s/ Mark Van De
      Laarschot


Mark
      Van De
      Laarschot





/s/ Patti L. Herrmann


Patti
      L.
      Herrmann


18


State
      Of
      Wisconsin  } }
      ss.


Brown
      County  }





Personally
      came
      before me this 4th day of December, A.D. 2006, Joseph P. O’Leary, to
      me known to be the Senior Vice President and Chief Financial Officer, and
      Barth J. Wolf, to me known to be the Secretary of the above-named Wisconsin
      Public
      Service Corporation ,
      the corporation
      described in and which executed the foregoing instrument, and to me known to
      be
      the persons who as such officers executed the foregoing instrument in the name
      and behalf of said corporation, and acknowledged the same, and acknowledged
      that
      the seal affixed to said instrument is the corporate seal of said corporation,
      and that they signed, sealed and delivered said instrument in the name and
      behalf of said corporation by authority of its Board of Directors and said
      Joseph P. O’Leary and Barth J. Wolf then and there acknowledged said
      instrument to be the free act and deed of said corporation by each of them
      voluntarily executed.




Given
      under my hand
      and notarial seal this 4th day of December, A.D. 2006.









/s/
      Kim M.
      Michiels


Kim
      M.
      Michiels


Notary
      Public,
      Brown County, Wisconsin


My
      commission expires:  May
      11,
      2008


(Notarial
      Seal)








19


State
      Of
      Wisconsin  }


}
      ss.


Brown
      County  }





Personally
      came
      before me this 4th day of December, A.D. 2006, Peter M. Brennan, to me
      known to be a Vice President of the above-named U.S.
      Bank National
      Association, the
      corporation
      described in and which executed the foregoing instrument, and to me known to
      be
      the person who as such officer executed the foregoing instrument in the name
      and
      behalf of said corporation, and acknowledged the same, and that he signed and
      delivered said instrument in the name and behalf of said corporation by
      authority of its Board of Directors and said Peter M. Brennan then and
      there acknowledged said instrument to be the free act and deed of said
      corporation by him voluntarily executed.




Given
      under my hand
      and notarial seal this 4th day of December, A.D. 2006.









/s/
      Kim M.
      Michiels


Kim
      M.
      Michiels


Notary
      Public,
      Brown County, Wisconsin


My
      commission expires:  May
      11,
      2008





(Notarial
      Seal)

































































This
      instrument was
      drafted by Attorney Larry J. Bonney of the law firm of Foley & Lardner LLP,
      Milwaukee, Wisconsin.


20




**SCHEDULE
      A**




The
      property
      referred to in Article II of the foregoing Supplemental Indenture from Wisconsin
      Public Service Corporation to U.S. Bank National Association (successor to
      Firstar Bank, National Association, successor to Firstar Trust Company, formerly
      known as First Wisconsin Trust Company), Trustee, dated as of August 1, 2006
      is
      that herein specifically described and enumerated or referred to in this
      Schedule A.




None








A-1