First Interstate BancSystem, Inc. is a financial holding company headquartered in Billings, Montana.

Instead, the Montana organization successfully negotiated to retain the well-known First Interstate name and logo.

[1] By the end of 1999, First Interstate had grown to 42 branches through a combination of de novo start-ups and acquisitions.

[1] In September 2021, First Interstate announced a merger with Sioux Falls, South Dakota–based Great Western Bank.

[4] The merger was completed on February 1, 2022, making Great Western an operating division of First Interstate Bank and extended the bank's presence into Arizona, Colorado and within the Midwest, with new locations in Iowa, Kansas, Minnesota, Missouri, Nebraska, North Dakota and South Dakota.