Johnston -- U.S. County in Oklahoma Population (2000): 10513 Housing Units (2000): 4782 Land area (2000): 644.504380 sq. miles (1669.258609 sq. km) Water area (2000): 13.780632 sq. miles (35.691672 sq. km) Total area (2000): 658.285012 sq. miles (1704.950281 sq. km) Located within: Oklahoma (OK), FIPS 40 Location: 34.278963 N, 96.678806 W Headwords: Johnston Johnston, OK Johnston County Johnston County, OK