There are 7 US Post Offices in Mills County serving a total of 14,699 residents equating to 2,100 residents per post office. It's estimated that approximately 23,461 packages are handled across the 7 county post offices annually. Mills County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 15,059. 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."