This Treasure State bank wants to be your treasury. First Interstate BancSystem is the holding company for First Interstate Bank, which has more than 70 branches in Montana, western South Dakota, and Wyoming. Serving area consumers, businesses, and municipalities, the bank provides traditional services, including deposit accounts, wealth management, and loans. Commercial loans, including mortgages, make up about half of the bank's loan portfolio; residential, agricultural, and construction loans round out its lending activities. First Interstate went public in 2010.