Seneca -- U.S. County in Ohio Population (2000): 58683 Housing Units (2000): 23692 Land area (2000): 550.587565 sq. miles (1426.015186 sq. km) Water area (2000): 1.781014 sq. miles (4.612806 sq. km) Total area (2000): 552.368579 sq. miles (1430.627992 sq. km) Located within: Ohio (OH), FIPS 39 Location: 41.128917 N, 83.173728 W Headwords: Seneca Seneca, OH Seneca County Seneca County, OH