First Midwest Bancorp, Inc. was headquartered in Chicago, Illinois, just east of O'Hare Airport.

In 2006, First Midwest acquired Bank Calumet for $307 million in cash, expanding its presence in the northwest Indiana area.

[5] On April 23, 2010, First Midwest Bank acquired Peotone Bank, taking on $130 million in assets and $127 million in deposits in a transaction facilitated by the Federal Deposit Insurance Corporation.

[6][7] On August 13, 2010, First Midwest acquired Palos Bank and Trust Company in a transaction facilitated by the Federal Deposit Insurance Corporation.

[10] The company acquired naming rights to the First Midwest Bank Amphitheatre in Tinley Park, Illinois.