Jefferson -- U.S. County in Ohio Population (2000): 73894 Housing Units (2000): 33291 Land area (2000): 409.608086 sq. miles (1060.880028 sq. km) Water area (2000): 1.265783 sq. miles (3.278364 sq. km) Total area (2000): 410.873869 sq. miles (1064.158392 sq. km) Located within: Ohio (OH), FIPS 39 Location: 40.360701 N, 80.725850 W Headwords: Jefferson Jefferson, OH Jefferson County Jefferson County, OH