formsc13g.htm
UNITED STATES
SECURITIES AND EXCHANGE COMMISSION
Washington, D.C. 20549
SCHEDULE 13G
Under the Securities Exchange Act of 1934
(Amendment No. N/A )*
First Interstate Bancsystem Inc.
(Name of Issuer)
Common Stock
(Title of Class of Securities)
32055Y201
(CUSIP Number)
December 31, 2010
(Date of Event Which Requires Filing of this Statement)
Check the appropriate box to designate the rule pursuant to which this Schedule is filed:
x Rule 13d-1(b)
o Rule 13d-1(c)
o Rule 13d-1(d)
* The remainder of this cover page shall be filled out for a reporting person's initial filing on this form with respect to the subject class of securities, and for any subsequent amendment containing information which would alter the disclosures provided in a prior cover page.
The information required in the remainder of this cover page shall not be deemed to be "filed" for the purpose of Section 18 of the Securities Exchange Act of 1934 ("Act") or otherwise subject to the liabilities of that section of the Act but shall be subject to all other provisions of the Act (however, see the Notes).
 
 
 
CUSIP No. 32055Y201            
           
1   NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
  Legg Mason Capital Management, Inc.
52-1268629
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
  (a) x
  (b) o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  Maryland
       
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH: 5   SOLE VOTING POWER
   
  0
     
6   SHARED VOTING POWER
   
  1,215,668
     
7   SOLE DISPOSITIVE POWER
   
  0
     
8   SHARED DISPOSITIVE POWER
   
  1,215,668
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  1,215,668
     
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  7.94%
     
12   TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
   
  IA , CO
   

FOOTNOTES
   
   
 
 
 
 
CUSIP No. 32055Y201            
           
1   NAMES OF REPORTING PERSONS
I.R.S. IDENTIFICATION NOS. OF ABOVE PERSONS (ENTITIES ONLY)
  Legg Mason Capital Management Special Investment Trust, Inc.
     
2   CHECK THE APPROPRIATE BOX IF A MEMBER OF A GROUP (SEE INSTRUCTIONS)
  (a) o
  (b) o
     
3   SEC USE ONLY
   
   
     
4   CITIZENSHIP OR PLACE OF ORGANIZATION
   
  Maryland
       
NUMBER OF SHARES BENEFICIALLY OWNED BY EACH REPORTING PERSON WITH: 5   SOLE VOTING POWER
   
  0
     
6   SHARED VOTING POWER
   
  950,000
     
7   SOLE DISPOSITIVE POWER
   
  0
     
8   SHARED DISPOSITIVE POWER
   
  950,000
     
9   AGGREGATE AMOUNT BENEFICIALLY OWNED BY EACH REPORTING PERSON
   
  950,000
     
10   CHECK IF THE AGGREGATE AMOUNT IN ROW (9) EXCLUDES CERTAIN SHARES (SEE INSTRUCTIONS)
   
  o
     
11   PERCENT OF CLASS REPRESENTED BY AMOUNT IN ROW (9)
   
  6.21%
     
12   TYPE OF REPORTING PERSON (SEE INSTRUCTIONS)
   
  IV, CO
   

FOOTNOTES
   
   
 
 
 
Item 1.

 
(a)
Name of Issuer
 
 
First Interstate Bancsystem, Inc.

 
(b)
Address of Issuer's Principal Executive Offices
 
 
401 North 31st Street
Billings, MT 59116

Item 2.

 
(a)
Name of Person Filing
 
 
Legg Mason Capital Management Inc.
Legg Mason Capital Management Special Investment Trust, Inc.

 
(b)
Address of Principal Business Office or, if none, Residence
 
 
100 International Drive
Baltimore, MD 21202

 
(c)
Citizenship
 
 
Maryland
Maryland

 
(d)
Title of Class of Securities
 
 
Common Stock

 
(e)
CUSIP Number
 
 
32055Y201

 
Item 3.
If this statement is filed pursuant to §§240.13d-1(b) or 240.13d-2(b) or (c), check whether the person filing is a:

 
(a)
o
Broker or dealer registered under section 15 of the Act (15 U.S.C. 78o).

 
(b)
o
Bank as defined in section 3(a)(6) of the Act (15 U.S.C. 78c).

 
(c)
o
Insurance company as defined in section 3(a)(19) of the Act (15 U.S.C. 78c).

 
(d)
o
Investment company registered under section 8 of the Investment Company Act of 1940 (15 U.S.C 80a-8).

 
(e)
x
An investment adviser in accordance with §240.13d-1(b)(1)(ii)(E);

 
(f)
o
An employee benefit plan or endowment fund in accordance with §240.13d-1(b)(1)(ii)(F);

 
(g)
o
A parent holding company or control person in accordance with § 240.13d-1(b)(1)(ii)(G);

 
(h)
o
A savings associations as defined in Section 3(b) of the Federal Deposit Insurance Act (12 U.S.C. 1813);

 
(i)
o
A church plan that is excluded from the definition of an investment company under section 3(c)(14) of the Investment Company Act of 1940 (15 U.S.C. 80a-3);

 
(j)
o
A non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J).

 
(k)
o
A group, in accordance with § 240.13d-1(b)(1)(ii)(K). If filing as a non-U.S. institution in accordance with § 240.13d-1(b)(1)(ii)(J), please specify the type of institution:

 
 
 
 
 
Item 4.
Ownership.
 
Provide the following information regarding the aggregate number and percentage of the class of securities of the issuer identified in Item 1.

 
(a)
Amount beneficially owned: 1,215,668

 
(b)
Percent of class: 7.94

 
(c)
Number of shares as to which the person has:

 
(i)
Sole power to vote or to direct the vote: 0

 
(ii)
Shared power to vote or to direct the vote: 1,215,668

 
(iii)
Sole power to dispose or to direct the disposition of: 0

 
(iv)
Shared power to dispose or to direct the disposition of: 1,215,668

Item 5.
Ownership of Five Percent or Less of a Class
 
If this statement is being filed to report the fact that as of the date hereof the reporting person has ceased to be the beneficial owner of more than five percent of the class of securities, check the following o .
 
N/A
 
Item 6.
Ownership of More than Five Percent on Behalf of Another Person.
 
Various accounts managed by the investment advisers identified in Item 8 have the right to receive or the power to direct the receipt of dividends from, or the proceeds from the sale of shares of the issuer.

The interest of Legg Mason Capital Management Special Investment Trust, Inc., an investment company registered under the Investment Company Act of 1940 and managed by Legg Mason Capital Management, Inc., amounted to 950,000 shares or 6.21% of the total shares outstanding.
 
Item 7.
Identification and Classification of the Subsidiary Which Acquired the Security Being Reported on By the Parent Holding Company
 
N/A
 
Item 8.
Identification and Classification of Members of the Group
 
N/A
 
Item 9.
Notice of Dissolution of Group
 
N/A
 
 
 
 
 
 
Item 10.
Certification
   
  By signing below I certify that, to the best of my knowledge and belief, the securities referred to above were acquired and are held in the ordinary course of business and were not acquired and are not held for the purpose of or with the effect of changing or influencing the control of the issuer of the securities and were not acquired and are not held in connection with or as a participant in any transaction having that purpose or effect.
 
 

SIGNATURE

After reasonable inquiry and to the best of my knowledge and belief, I certify that the information set forth in this statement is true, complete and correct.
  Legg Mason Capital Management, Inc.
  
       
Date: February 15, 2011
By:
/s/ Nicholas C. Milano  
    Name: Nicholas C. Milano  
    Title: Chief Compliance Officer  
       
  Legg Mason Capital Management Special Investment Trust, Inc.
 
       
Date: February 15, 2011
By:
/s/ Richard M. Wachterman  
    Name: Richard M. Wachterman  
    Title: Assistant Secretary  
       
Footnotes:
This Joint Filing Agreement confirms the agreement by and among the undersigned that the Schedule 13G is filed on behalf of each of the reporting person(s)
identified below.

Legg Mason Capital Management, Inc.

By: /s/ Nicholas C. Milano
Nicholas C. Milano
Chief Compliance Officer



Legg Mason Capital Management Special Investment Trust, Inc.

By: /s/ Richard M. Wachterman 
Richard M. Wachterman
Assistant Secretary

Attention:
Intentional misstatements or omissions of fact constitute Federal criminal violations (See 18 U.S.C. 1001)