Jefferson -- U.S. County in Colorado Population (2000): 527056 Housing Units (2000): 212488 Land area (2000): 772.093977 sq. miles (1999.714135 sq. km) Water area (2000): 5.967159 sq. miles (15.454869 sq. km) Total area (2000): 778.061136 sq. miles (2015.169004 sq. km) Located within: Colorado (CO), FIPS 08 Location: 39.727160 N, 105.142196 W Headwords: Jefferson Jefferson, CO Jefferson County Jefferson County, CO