 Land grants issued by the agents of the English kings and by agents of the Northern Neck (Fairfax) Proprietary are housed in the archives of the Library of Virginia in Richmond, Virginia, and are available online at the Library of Virginia website.According to the U.S. Census Bureau, the county has a total area of , of which is land and (0.3%) is water.The Rappahannock River forms the northeastern boundary and separates Rappahannock County from Fauquier County.