In 1649, King Charles II of England granted all of the land between the Rappahannock and Potomac Rivers to a group of seven Englishmen. Eventually, in 1719, this land came into the possession of Thomas, sixth Lord Fairfax, after whom Fairfax County was named. By 1732 there were attempts to form the land into a county, but it was not until 1741 that the Virginia Assembly, meeting in Williamsburg, created Fairfax County.
In 1757, the northwestern two-thirds of Fairfax became Loudoun County. A part of Fairfax County was ceded to form Alexandria County of the District of Columbia in 1789, but was returned to Virginia in 1846, and renamed Arlington County in 1920. Alexandria became an independent city in 1870, Falls Church in 1948, and the town of Fairfax became an independent city in 1961. Source History of Fairfax County, Virginia
Loudoun, Prince William, and Arlington counties as well as the independent cities of Fairfax, Falls Church and Alexandria. Across the Potomac River in Maryland, adjacent counties are Charles, Prince George's and Montgomery.