King George County is a county located in the Commonwealth of Virginia. As of the 2010 census, the population was 23,584. Its county seat is King George. The county's largest employer is the U.S. Naval Surface Warfare Center Dahlgren Division. It is adjacent to the two-lane, 2-mile long Harry W. Nice Memorial Bridge carrying U.S. Highway 301 over the Potomac River. It contains the ZIP codes 22448 and 22485 (all other areas within King George).