First Interstate BancSystem, Inc. (NASDAQ:FIBK) (“First Interstate”), parent company of First Interstate Bank, and Mountain West Financial Corp. (OTCBB:MTWF) (“Mountain West”), parent company of Mountain West Bank, National Association (“Mountain West Bank”), announced today that the Federal Reserve has approved the application by First Interstate and Mountain West to complete the acquisition by merger of Mountain West by First Interstate, subject to a 15-day waiting period as required by the U.S. Department of Justice. In order to coordinate an orderly completion of the merger transaction following the expiration of the waiting period, First Interstate and Mountain West have agreed upon a closing date for the merger of July 31, 2014, after the close of business. Subject to receipt of necessary further regulatory approvals, First Interstate is targeting and expects the subsequent merger of Mountain West Bank into First Interstate Bank will occur on October 18, 2014. Notice of Merger Consideration Election Statement Submission Deadline As previously disclosed to the Mountain West stockholders in the merger agreement and related proxy statement/prospectus mailed to them in connection with the merger, Mountain West stockholders may elect – prior to the election deadline and subject to the other terms of the merger agreement – to receive for their shares of Mountain West common stock in the merger either all cash or all Class A common stock of First Interstate (in lieu of the cash and stock combination otherwise established for the merger consideration). Pursuant to the merger agreement, electing Mountain West stockholders must submit to the exchange agent for the merger their election statements before 5:00 p.m., Mountain Time, on the date that is five business days prior to the closing date of the merger. Election statements and related submission instructions have been previously provided to the Mountain West stockholders. In connection with the foregoing, notice is hereby given to the Mountain West stockholders that the election deadline to submit timely election statements to the exchange agent has been determined to be 5:00 p.m., Mountain Time, on July 24, 2014. Each of First Interstate and Mountain West will also post the date of the election deadline on its web site. About First Interstate BancSystem, Inc. First Interstate is a financial services holding company, headquartered in Billings, Montana, with $7.6 billion in assets as of March 31, 2014. It is the parent company of First Interstate Bank, a community bank operating 75 banking offices, along with online and mobile banking services, throughout Montana, Wyoming and South Dakota. As a recognized leader in community banking services with 25 consecutive years of profitability, First Interstate’s culture is driven by strong family and corporate values, as well as a commitment to long-term organic growth, exemplary customer service, exceeding customer expectations through its products and services and supporting, with leadership and resources, the communities it serves.