Union -- U.S. County in Illinois Population (2000): 18293 Housing Units (2000): 7894 Land area (2000): 416.160883 sq. miles (1077.851694 sq. km) Water area (2000): 5.966986 sq. miles (15.454421 sq. km) Total area (2000): 422.127869 sq. miles (1093.306115 sq. km) Located within: Illinois (IL), FIPS 17 Location: 37.461737 N, 89.248116 W Headwords: Union Union, IL Union County Union County, IL