Mercer -- U.S. County in Missouri Population (2000): 3757 Housing Units (2000): 2125 Land area (2000): 454.175881 sq. miles (1176.310082 sq. km) Water area (2000): 1.001537 sq. miles (2.593970 sq. km) Total area (2000): 455.177418 sq. miles (1178.904052 sq. km) Located within: Missouri (MO), FIPS 29 Location: 40.428383 N, 93.577593 W Headwords: Mercer Mercer, MO Mercer County Mercer County, MO