Decatur -- U.S. County in Iowa Population (2000): 8689 Housing Units (2000): 3833 Land area (2000): 531.803590 sq. miles (1377.364917 sq. km) Water area (2000): 1.516077 sq. miles (3.926620 sq. km) Total area (2000): 533.319667 sq. miles (1381.291537 sq. km) Located within: Iowa (IA), FIPS 19 Location: 40.727585 N, 93.789690 W Headwords: Decatur Decatur, IA Decatur County Decatur County, IA