Clay -- U.S. County in Kansas Population (2000): 8822 Housing Units (2000): 4084 Land area (2000): 643.841746 sq. miles (1667.542397 sq. km) Water area (2000): 11.599568 sq. miles (30.042743 sq. km) Total area (2000): 655.441314 sq. miles (1697.585140 sq. km) Located within: Kansas (KS), FIPS 20 Location: 39.357193 N, 97.146911 W Headwords: Clay Clay, KS Clay County Clay County, KS