There are 8 US Post Offices in Decatur County serving a total of 8,597 residents equating to 1,075 residents per post office. It's estimated that approximately 13,722 packages are handled across the 8 county post offices annually. Decatur County is a county located in the U.S. state of Iowa. As of the 2010 census, the population was 8,457. The county seat is Leon. This county is named for Stephen Decatur, Jr., a hero in the War of 1812."