King William County was established by an enabling act of Virginia General Assembly effective on April 11, 1702. King William County was created from the Pamunkey Neck section of King and Queen County (Town of West Point incorporated on July 11, 1870). King William is also home to many historic homes and estates spanning the 17th, 18th, and 19th centuries, including Chelsea Plantation, Elsing Green, Horn Quarter, Mount Columbia, and Burlington.

King William County is managed by a county administrator, who reports to a five-member Board of Supervisors. The Board's regular meetings are held in the Board Room of the King William County Administration Building, 180 Horse Landing Road, and are scheduled on the fourth Monday of every month (with possible exceptions in May, November and December due to holidays) at 7 p.m. These meetings are open to the public.