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EXHIBIT 4.2(z)    
  

NORTHWESTERN ENERGY, L.L.C.  

 AND  

 NORTHWESTERN CORPORATION  

 TO  

 THE BANK OF NEW YORK  

 Trustee  

SECOND SUPPLEMENTAL INDENTURE

(For Unsecured Subordinated Debt Securities

relating to Trust Securities)  

 Dated as of August 13, 2002  

        SECOND SUPPLEMENTAL INDENTURE, dated as of August 13, 2002 (this "Second Supplemental
Indenture"), among NORTHWESTERN ENERGY, L.L.C., a limited liability company duly organized and existing under the laws of the
State of Montana, formerly known as The Montana Power, L.L.C. and successor by merger to The Montana Power Company (the "Company"), having its principal
office at 40 East Broadway, Butte, Montana 59701, NORTHWESTERN CORPORATION, a corporation duly organized and existing under the laws of the State of
Delaware, having its principal office at 125 S. Dakota Avenue, Sioux Falls, South Dakota 57104 ("NOR"), and THE BANK OF NEW
YORK, a corporation duly organized and existing as a banking corporation under the laws of the State of New York, having its principal corporate trust office at 101 Barclay
Street, New York, New York 10286, as Trustee (the "Trustee"), supplementing the Indenture, dated as of November 1996, between The Montana Power
Company, predecessor to the Company, and the Trustee, as amended by the First Supplemental Indenture, dated as of February 13, 2002, between the Company (formerly known as The Montana Power,
L.L.C.) and the Trustee (as supplemented, the "Indenture"). 

RECITALS  

        WHEREAS, pursuant to a Unit Purchase Agreement, dated as of September 29, 2000, by and between NOR, Touch America Holdings, Inc. and The Montana
Power Company, on February 15, 2002, NOR acquired all the outstanding membership interests in the Company and the Company became a direct wholly-owned subsidiary of NOR; and 

        WHEREAS,
as of the date hereof, $67,010,325 aggregate principal amount of the Company's 8.45% Junior Subordinated Debentures due December 31, 2036 are the only Securities
Outstanding under the Indenture (the "QUIPS Debentures"); 

        WHEREAS,
NOR now desires to enter into this Second Supplemental Indenture to fully and unconditionally assume, on a joint and several basis with the Company, the Company's obligations
with respect to the Outstanding QUIPS Debentures and the performance of every covenant, obligation and agreement of the Company under the Indenture applicable to the Outstanding QUIPS Debentures to be
performed or observed as though each such covenant, obligation and agreement were applicable directly to NOR (substituting NOR for the Company for purposes of the Indenture), which assumption shall be
subject to all of the terms and conditions related to the QUIPS Debentures contained herein, in the Indenture and in the QUIPS Debentures, including, without limitation, the subordination of the
obligations so assumed to all Senior Indebtedness of NOR (substituting NOR for the Company for purposes of the definition of Senior Indebtedness) to the same extent as such QUIPS Debentures are
subordinated to all Senior Indebtedness of the Company, and which assumption shall remain in effect only for so long as any of the QUIPS Debentures, which are outstanding on the date hereof, shall
remain Outstanding; and 

        WHEREAS,
Section 1201(b) of the Indenture permits the parties thereto to enter into a supplemental indenture without the consent of Holders to add provisions to the Indenture for
the benefit of all Holders or for the benefit of the Holders of, or to remain in effect only so long as there shall be Outstanding, Securities of one or more specified series; and 

        WHEREAS,
the assumption by NOR of the obligations of the Company with respect to the QUIPS Debentures under the Indenture will benefit the Holders of the Outstanding QUIPS Debentures;
and 

        WHEREAS,
the Company and NOR have duly authorized the execution and delivery of this Second Supplemental Indenture pursuant to Section 1201(b) of the Indenture; and 

        WHEREAS,
the Company and NOR have requested the Trustee join with them in the execution of this Second Supplemental Indenture. 

 

        NOW,
THEREFORE, in consideration of the mutual covenants and agreements contained herein and for other good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereto, intending to be legally bound, hereby agree as follows: 

ARTICLE ONE  

 Additional Obligor.  

        Section 101.    As of the date hereof, NOR fully and unconditionally assumes, on a joint and several basis with the
Company, the due and punctual payment of the principal of and premium, if any, and interest, if any, on all Outstanding QUIPS Debentures and the performance of every covenant, obligation and agreement
of the Company under the Indenture applicable to the Outstanding QUIPS Debentures to
be performed or observed as though each such covenant, obligation and agreement were applicable directly to NOR (substituting NOR for the Company for purposes of the Indenture), which assumption shall
be subject to all of the terms and conditions related to the QUIPS Debentures contained herein, in the Indenture and in the QUIPS Debentures, including, without limitation, the subordination of such
obligations to all Senior Indebtedness of NOR (substituting NOR for the Company for purposes of the definition of Senior Indebtedness) to the same extent as such QUIPS Debentures are subordinated to
all Senior Indebtedness of the Company. The assumption contained in this Second Supplemental Indenture shall remain in effect only for so long as any of the QUIPS Debentures, which are Outstanding on
the date hereof, shall remain Outstanding. Notwithstanding the assumption contained in this Second Supplemental Indenture, the obligations of the Company to duly and punctually pay the principal of
and premium, if any, and interest, if any, on the Outstanding QUIPS Debentures and to perform its covenants, obligations and agreements on the part of the Company under the Indenture shall remain in
full force and effect, without diminution or derogation in any respect whatsoever. 

ARTICLE TWO  

 Rights of Parties Not Prejudiced.  

        Section 201.    Notwithstanding the foregoing, the assumption contained in this Second Supplemental Indenture shall be
without prejudice to any rights of each of the Company and NOR under the QUIPs Debentures, the Indenture and this Second Supplemental Indenture, including, without limitation, the right of each of the
Company and NOR to consolidate with or merge into any other corporation, or convey or otherwise transfer, or lease, its properties and assets substantially as an entirety to any Person, and to be
relieved from its obligations under the QUIPS Debenture, the Indenture and hereunder, as provided in Article Eleven of the Indenture. For the avoidance of doubt, the Company may consolidate with or
merge into NOR or convey or otherwise transfer, or lease, its properties and assets substantially as an entirety to NOR, and be relieved of its obligations under the QUIPS Debentures, the Indenture
and hereunder as provided in Article Eleven of the Indenture notwithstanding the fact that NOR has assumed the Company's obligations under the QUIPS Debentures and the Indenture pursuant to this
Second Supplemental Indenture, and such assumption hereunder is expressly subject to such right. 

ARTICLE THREE  

 Miscellaneous Provisions.  

        Section 301.    The terms defined in the Indenture shall, for all purposes of this Second Supplemental Indenture, have
the meaning specified in the Indenture. 

        Section 302.    The Trustee hereby accepts the trusts herein declared, provided, created or supplemented and agrees to
perform the same upon the terms and conditions herein and in the 

2

 

Indenture set forth; provided, however, that the Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or
sufficiency of this Second Supplemental Indenture or for or in respect of the recitals contained herein, all of which recitals are made solely by the Company and NOR. 

        Section 303.    Each and every term and condition contained in this Second Supplemental Indenture shall apply to and form
part of the Indenture with the same force and effect as if the same were set forth in full with such omissions, variations and insertions, if any, as may be appropriate to make the same conform to the
provisions of this Second Supplemental Indenture and each and every term and condition contained in Article Nine of the Indenture shall apply to and form part of this Second Supplemental Indenture
with the same force and effect as if the same were set forth in full herein. 

        Section 304.    Whenever in this Second Supplemental Indenture any of the parties hereto is named or referred to, this
shall, subject to the provisions of the Indenture, be deemed to include the successors and assigns of such respective parties, and all the covenants and agreements in this Second Supplemental
Indenture contained by or on behalf of the Company, NOR or the Trustee shall, subject as aforesaid, bind and inure to the respective benefits of the respective successors and assigns of such parties,
whether so expressed or not. 

        Section 305.    Nothing in this Second Supplemental Indenture, expressed or implied, is intended, or shall be construed,
to confer upon, or to give to, any person, firm or corporation, other than the parties hereto and the Holders of the QUIPS Debentures Outstanding under the Indenture, as amended and supplemented, any
right, remedy or claim under or by reason of this Second Supplemental Indenture or any covenant, condition, stipulation, promise or agreement hereof, and all the covenants, conditions, stipulations,
promises and agreements in this Second Supplemental Indenture contained by or on behalf of respective parties shall be for the sole and exclusive benefit of the parties hereto, and of the Holders of
the QUIPS Debentures Outstanding under the Indenture. 

        Section 306.    This Second Supplemental Indenture may be executed in several counterparts, each of which shall be deemed
to be an original and all of which shall constitute but one and the same instrument. 

        Section 307.    Except as set forth in this Second Supplemental Indenture, all of the provisions of the Indenture remain
in full force and effect, unamended. 

        Section 308.    This Second Supplemental Indenture shall be governed by and construed in accordance with the laws of the
State of New York, except to the extent that the law of any other jurisdiction shall be mandatorily applicable. 

        Section 309.    In case any one or more of the provisions contained in this Second Supplemental Indenture shall for any
reason be held to be invalid, illegal or unenforceable in any respect, such invalidity, illegality or unenforceability shall not affect any other provisions of this Second Supplemental Indenture, but
this Second Supplemental Indenture shall be construed as if such invalid or illegal or unenforceable provision had never been contained herein or therein. 

3

        IN WITNESS WHEREOF, the parties hereto have caused this Second Supplemental Indenture to be duly executed, and their respective seals to be hereunto affixed attested, all as of the day
and year first above written. 

	[Seal]	 	NORTHWESTERN ENERGY, L.L.C.
	

 	
 	

By:	

/s/  MICHAEL J. HANSON      
	 	 	 	
 Michael J. Hanson

President and Chief Executive Officer
	

ATTEST:	
 	

 	

 
	

 	
 	

 	

 
	/s/  ALAN D. DIETRICH      
 Alan D. Dietrich

Secretary	 	 	 
	

[Seal]	
 	

NORTHWESTERN CORPORATION
	

 	
 	

By:	

/s/  KIPP D. ORME      
	 	 	 	
 Kipp D. Orme

Vice President and Chief Financial Officer
	

ATTEST:	
 	

 	

 
	

 	
 	

 	

 
	/s/  ALAN D. DIETRICH      
 Alan D. Dietrich

Vice President—Legal Administration and Corporate Secretary	 	 	 
	

[Seal]	
 	

THE BANK OF NEW YORK, its Trustee
	

 	
 	

By:	

/s/  MARYBETH A. LEWICKI      
	 	 	 	
 MaryBeth A. Lewicki

Vice President
	

ATTEST:	
 	

 	

 
	

 	
 	

 	

 
	/s/        
 Name:

Title:	 	 	 

	STATE OF MONTANA	)
	 	) ss.:
	COUNTY OF SILVER BOW	)

        On
the 13th day of August, 2002, before me personally came David A. Monaghan, to me known, who, being by me duly sworn, did depose and say that she/he is Chief Financial Officer of
NorthWestern Energy, L.L.C., the limited liability company described in and which executed the foregoing instrument; and that she/he signed her/his name thereto. 

        IN
WITNESS WHEREOF, I have hereunto set my hand and affixed my seal of office this 13th day of August, 2002. 

	 	 
	 	/s/  KAREN L. SMOOK      
	 	

	STATE OF SOUTH DAKOTA	)
	 	) ss.:
	COUNTY OF MINNEHHA	)

        On
the 13th day of August, 2002, before me personally came Kipp D. Orme, to me known, who, being by me duly sworn, did depose and say that she/he is Vice President and Chief Financial
Officer of NorthWestern Corporation, one of the corporations described in and which executed the foregoing instrument; that she/he knows the seal of said corporation; that the seal affixed to said
instrument is such corporate seal; that it was so affixed by authority of the Board of Directors of said corporation; and that she/he signed her/his name thereto by like authority. 

        IN
WITNESS WHEREOF, I have hereunto set my hand and affixed my seal of office this 13th day of August, 2002. 

	 	 
	 	/s/  KAREN L. SMOOK      
	 	

	STATE OF NEW YORK	)
	 	) ss.:
	COUNTY OF NEW YORK	)

        On
the 13th day of August, 2002, before me personally came MaryBeth A. Lewicki, to me known, who, being by me duly sworn, did depose and say that she is a Vice President of The Bank of
New York, one of the corporations described in and which executed the foregoing instrument; that she knows the seal of said corporation; that the seal affixed to said instrument is such corporate
seal; that it was so affixed by authority of the Board of Directors of said corporation; and that she signed her name thereto by like authority. 

        IN
WITNESS WHEREOF, I have hereunto set my hand and affixed my seal of office this 13th day of August, 2002. 

	 	 
	 	/s/        
	 	

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EXHIBIT 4.2(z)QuickLinks
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Exhibit 4.2(aa)    
  

Execution Version  

 NORTHWESTERN CORPORATION

(Successor To Northwestern Energy, L.L.C.,

Formerly Known As The Montana Power, L.L.C.)  

TO  

THE BANK OF NEW YORK

Trustee  

THIRD SUPPLEMENTAL INDENTURE

(For Unsecured Subordinated Debt Securities

relating to Trust Securities)  

Providing,
among other things, for the assumption by NorthWestern Corporation

of the due and punctual payment of the principal of and premium, if any,

and interest, if any, on all Outstanding Securities and the performance of every

covenant and condition of NorthWestern Energy, L.L.C. under the Indenture. 

Dated
as of November 15, 2002 

        THIRD SUPPLEMENTAL INDENTURE, dated as of November 15, 2002, between NORTHWESTERN CORPORATION, a Delaware corporation (herein called
"NorthWestern"), having its principal office at 125 S. Dakota Avenue Sioux Falls, SD 57104, and THE BANK OF NEW YORK, a corporation
duly organized and existing as a banking corporation under the laws of the State of New York, having its principal corporate trust office at 101 Barclay Street, New York, New York 10286, as
Trustee (herein called the "Trustee"), supplementing the Indenture, dated as of November 1, 1996, between The Montana Power Company, a
corporation organized under the laws of the State of Montana ("MPC"), and the Trustee (the "Indenture"),
such Indenture having been previously supplemented by the First Supplemental Indenture, dated as of February 13, 2002, and the Second Supplemental Indenture dated as of August 13, 2002,
both by and between the Trustee and NorthWestern Energy, L.L.C. (formerly known as The Montana Power L.L.C.), a limited liability company duly organized and existing under the laws of the State
of Montana (herein called "NorthWestern Energy") and successor by merger to MPC. 

RECITALS  

        WHEREAS, MPC entered into an Agreement and Plan of Merger among MPC, Touch America Holdings, Inc. (a Delaware corporation and a wholly-owned subsidiary of
MPC), and NorthWestern Energy, dated as of February 20, 2001, pursuant to which MPC was merged with and into NorthWestern Energy; and 

        WHEREAS,
NorthWestern Energy duly authorized the execution and delivery of a First Supplemental Indenture, dated as of February 13, 2002, pursuant to Sections 1101(a) and 1201 of
the Indenture, to evidence the succession of NorthWestern Energy to MPC, and the assumption by NorthWestern Energy of the covenants of MPC contained in the Indenture and the Securities issued
thereunder; 

        WHEREAS,
NorthWestern Energy and NorthWestern entered into an Asset and Stock Transfer Agreement, dated as of November 15, 2002, pursuant to which the property and assets of
NorthWestern Energy substantially as an entirety have been transferred to NorthWestern and NorthWestern has assumed substantially all of the liabilities of NorthWestern Energy; 

        WHEREAS,
NorthWestern duly authorized the execution and delivery of this Third Supplemental Indenture pursuant to Sections 1101(a) and 1201 of the Indenture, to evidence the succession
of NorthWestern to NorthWestern Energy and the assumption by NorthWestern of the covenants of NorthWestern Energy contained in the Indenture and the Securities issued thereunder; 

        WHEREAS,
NorthWestern Energy has requested the Trustee join with NorthWestern in the execution of this Third Supplemental Indenture; 

        NOW,
THEREFORE, THIS THIRD SUPPLEMENTAL INDENTURE WITNESSETH: 

 

        For
and in consideration of the premises, it is mutually covenanted and agreed, for the equal and proportionate benefit of all Holders of the Securities or of any series thereof, as
follows: 

 
 

ARTICLE ONE
  
    Covenants and Agreements of NorthWestern.    
  

        Section 101.    NorthWestern hereby expressly assumes the due and punctual payment of the principal of and premium, if
any, and interest, if any, on all Outstanding Securities issued under the Indenture and the performance of every covenant of the Indenture on the part of NorthWestern Energy to be performed or
observed. 

 
 

ARTICLE TWO
  
    Section 201. Miscellaneous Provisions.    
  

        Section 1.    The terms defined in the Indenture shall, for all purposes of this Third Supplemental Indenture, have the meaning specified in the
Indenture. 

        Section 2.    The
Trustee hereby accepts the trusts herein declared, provided, created or supplemented and agrees to perform the same upon the terms and conditions
herein and in the Indenture set forth and upon the following terms and conditions: 

        The
Trustee shall not be responsible in any manner whatsoever for or in respect of the validity or sufficiency of this Third Supplemental Indenture or for or in respect of the recitals
contained herein, all of which recitals are made by NorthWestern solely. In general, each and every term and condition contained in this Third Supplemental Indenture shall apply to and form part of
the Indenture with the same force and effect as if the same were set forth in full with such omissions, variations and insertions, if any, as may be appropriate to make the same conform to the
provisions of this Third Supplemental Indenture. 

        Section 3.    Whenever
in this Third Supplemental Indenture any of the parties hereto is named or referred to, this shall, subject to the provisions of the Indenture, be
deemed to include the successors and assigns of such respective parties, and all the covenants and agreements in this Third Supplemental Indenture contained by or on behalf of Northwestern, or by or
on behalf of the Trustee shall, subject as aforesaid, bind and inure to the respective benefits of the respective successors and assigns of such parties, whether so expressed or not. 

        Section 4.    Nothing
in this Third Supplemental Indenture, expressed or implied, is intended, or shall be construed, to confer upon, or to give to, any person, firm or
corporation, other than the parties hereto and the holders of the Outstanding Securities under the Indenture, as amended and supplemented, any right, remedy or claim under or by reason of this Third
Supplemental Indenture or any covenant, condition, stipulation, promise or agreement hereof, and all the covenants, conditions, stipulations, promises and agreements in this Third Supplemental
Indenture contained by or on behalf of respective parties shall be for the sole and exclusive benefit of the parties hereto, and of the Holders of the Securities now or to be Outstanding under the
Indenture. 

        Section 5.    This
Third Supplemental Indenture may be executed in several counterparts, each of which shall be deemed to be an original and all of which shall
constitute but one and the same instrument. 

[Signature
Pages to Follow] 

2

        IN
WITNESS WHEREOF, the parties hereto have caused this Indenture to be duly executed, and their respective seals to be hereunto affixed attested, all as of the day and year first above
written. 

	[Seal]	 	 	 	NORTHWESTERN CORPORATION
	

 	
 	

 	
 	
By:	
 	

/s/  ERIC R. JACOBSEN      

	 	 	 	 	 	 	Name:	 	Eric R. Jacobsen
	 	 	 	 	 	 	Title:	 	SVP, General Counsel and CLO
	

ATTEST:	
 	

 	
 	

 	
 	

 
	

/s/  MICHAEL J. YOUNG      
	
 	

 	
 	

 	
 	

 
	Name:	 	Michael J. Young	 	 	 	 	 	 
	Title:	 	Assistant Secretary	 	 	 	 	 	 

	

[Seal]	
 	

 	
 	
THE BANK OF NEW YORK, Trustee
	

 	
 	

 	
 	

By:	
 	

	 	 	 	 	 	 	Name:	 	    
	 	 	 	 	 	 	Title:	 	    
	

ATTEST:	
 	

 	
 	

 	
 	

 
	

	
 	

 	
 	

 	
 	

 
	Name:	 	    	 	 	 	 	 	 
	Title:	 	    	 	 	 	 	 	 

	 
	 

	STATE OF SOUTH DAKOTA	)
	 	) ss.:
	COUNTY OF MINNEHAHA	)

        On
the 12th day of November, 2002, before me personally came Eric R. Jacobsen, to me known, who, being by me duly sworn, did depose and say that he is SVP, General Counsel and CLO
of NorthWestern Corporation, the corporation described in and which executed the foregoing instrument; that he knows the seal of said company; that the seal affixed to said instrument is such
corporate seal; that it as so affixed by authority of the Board of Directors of said company, and that he signed his name thereto by like authority. 

	

 	
 	

 	
 	

 	
 	

/s/  KAREN L. SMOOK      

	 	 	 	 	 	 	Karen L. Smook

My Commission expires: 7-12-2005

        IN
WITNESS WHEREOF, the parties hereto have caused this Indenture to be duly executed, and their respective seals to be hereunto affixed attested, all as of the day and year first above
written. 

	[Seal]	 	 	 	NORTHWESTERN CORPORATION
	

 	
 	

 	
 	
By:	
 	

	 	 	 	 	 	 	Name:	 	    
	 	 	 	 	 	 	Title:	 	    
	

ATTEST:	
 	

 	
 	

 	
 	

 
	

	
 	

 	
 	

 	
 	

 
	Name:	 	    	 	 	 	 	 	 
	Title:	 	    	 	 	 	 	 	 

	

[Seal]	
 	

 	
 	
THE BANK OF NEW YORK, Trustee
	

 	
 	

 	
 	

By:	
 	

/s/  MARYBETH LEWICKI      

	 	 	 	 	 	 	Name:	 	MaryBeth Lewicki
	 	 	 	 	 	 	Title:	 	Vice President
	

ATTEST:	
 	

 	
 	

 	
 	

 
	

/s/  STACEY B. POINDEXTER      
	
 	

 	
 	

 	
 	

 
	Name:	 	Stacey B. Poindexter	 	 	 	 	 	 
	Title:	 	Assist. Treasurer	 	 	 	 	 	 

	 
	 

	

STATE OF NEW YORK	

)
	 	) ss.:
	COUNTY OF NEW YORK	)

        On
this 15th day of November, 2002, before me, William Cassels, a Notary Public in and for the State of New York, personally came and appeared MaryBeth Lewicki, to me known and known to
me to be a/the Vice President of THE BANK OF NEW YORK, the corporation that executed the within instrument, and acknowledged to me that such corporation executed the same, and, being by me duly sworn,
did depose and say that she/he resides at Staten Island, NY; that she/he is a/the Vice President of THE BANK OF NEW YORK, the corporation described in and which executed the within and above
instrument; that she/he knows the seal of said corporation; that the seal affixed to said instrument is such corporate seal; that it was so affixed by authority of the Board of Directors of said
corporation, and that she/he signed her/his name thereto by like authority. 

        IN
WITNESS WHEREOF, I have hereunto subscribed my name and affixed my official seal the day and year in this certificate first above written. 

	

 	
 	

 	
 	

 	
 	

/s/  WILLIAM J. CASSELS      

	 	 	 	 	 	 	William J. Cassels

Notary Public, State of New York

No. 01CA5027729

Qualified in Bronx County

Commission Expires May 18, 2006

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Exhibit 4.2(aa)

ARTICLE ONE Covenants and Agreements of NorthWestern.

ARTICLE TWO Section 201. Miscellaneous Provisions.

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