Mills County is a county located in the U.S. state of Iowa. As of the 2020 census, the population was 14,484. The county seat is Glenwood. The county was formed in 1851 and named for Major Frederick Mills of Burlington, Iowa, who was killed at the Battle of Churubusco during the Mexican–American War. Mills County is included in the Omaha–Council Bluffs, NE–IA Metropolitan Statistical Area.