Investor Presentation Filed by First Interstate BancSystem, Inc. pursuant to Rule 425 under the Securities Act of 1933 Subject Company: Great Western Bancorp, Inc. Commission File No. 001-36688 Date: January 27, 2022 January 2022 CAUTIONARY NOTE REGARDING FORWARD-LOOKING STATEMENTS This presentation contains "forward-looking statements" within the meaning of Section 27A of the Securities Act of 1933, as amended, and Rule 175 promulgated thereunder, and Section 21E of the Securities Exchange Act of 1934, as ...