Exhibit 10.21
TERMINATION OF CREDIT AGREEMENT
          This Termination is entered into as of January 10, 2008 by and between
First Interstate BancSystem, Inc., a Montana corporation (the “Borrower”), and
Wells Fargo Bank, National Association, a national banking association (the
“Bank”).
          The Borrower and the Bank are parties to a Credit Agreement dated
June 30, 2005, setting forth the terms on which the Bank may make advances to
the Borrower during a period ending June 30, 2008 (the “Existing Credit
Agreement”).
          Concurrent with the execution of this Termination, the parties are
entering into a separate Credit Agreement, dated the date hereof, setting forth
the terms on which the Lenders (as defined therein) may make advances to the
Borrower (the “New Credit Agreement”). The New Credit Agreement is intended to
supersede the Existing Credit Agreement, and the parties accordingly wish to
terminate their obligations under the Existing Credit Agreement.
          Accordingly, in consideration of the mutual covenants contained in the
Existing Credit Agreement, the New Credit Agreement and this Termination, the
parties hereby agree as follows:
          1. As used herein, “Effective Time” means the time at which the first
advance or other extension of credit is made under the New Credit Agreement.
          2. As of the Effective Time, the Bank shall have no further obligation
to make advances under the Existing Credit Agreement, and the Borrower shall
repay all obligations outstanding under the Existing Credit Agreement, whether
from the proceeds of advances under the New Credit Agreement or otherwise.
          3. Nothing herein shall terminate any obligation that, by its express
terms or by its nature, survives termination of the Existing Credit Agreement,
including but not limited to any indemnification obligation and any obligation
under Section 7.3 (“Costs, Expenses and Attorneys’ Fees”) of the Existing Credit
Agreement.
          4. This Termination may be executed in any number of counterparts,
each of which when so executed and delivered shall be deemed to be an original
and all of which counterparts of this Termination, taken together, shall
constitute but one and the same instrument.
          IN WITNESS WHEREOF, the parties hereto have executed this Agreement as
of the day and year first above-written.

                      FIRST INTERSTATE BANCSYSTEM, INC.       WELLS FARGO BANK,
NATIONAL ASSOCIATION    
 
                   
By
  /s/ TERRILL R. MOORE       By   /s/ CYNTHIA M. SPAGNOLA    
 
                   
 
  Name: Terrill R. Moore           Name: Cynthia M. Spagnola    
 
  Title: Executive Vice President and Chief
             Financial Officer           Title: Vice President