 The land upon which Valley later developed was originally part of the South Branch Survey of Thomas Fairfax , 6th Lord Fairfax of Cameron 's Northern Neck Proprietary . The South Branch Survey extended from the north end of The Trough to the confluence of the north and south branches of the Potomac River . Lord Fairfax originally planned to maintain the South Branch Survey as his personal manor , but later commissioned James Genn to survey the South Branch Potomac River lowlands for sale and lease in 1748 , with land lots ranging in size from 300 acres ( 120 ha ) to 400 acres ( 160 ha ) . Valley was located within the northern section of Lot Number 17 of the South Branch Survey , which Lord Fairfax granted to Samuel Earle in 1749 . Earle was a gentleman from Frederick County , Virginia . 
