De Witt -- U.S. County in Illinois Population (2000): 16798 Housing Units (2000): 7282 Land area (2000): 397.575757 sq. miles (1029.716440 sq. km) Water area (2000): 7.578630 sq. miles (19.628562 sq. km) Total area (2000): 405.154387 sq. miles (1049.345002 sq. km) Located within: Illinois (IL), FIPS 17 Location: 40.178001 N, 88.914787 W Headwords: De Witt De Witt, IL De Witt County De Witt County, IL