Fort Belvoir /ˈbɛlvwɑːr/ is a United States Army installation and a census-designated place in Fairfax County, Virginia, United States. It was developed on the site of the former Belvoir plantation, seat of the prominent Fairfax family for whom Fairfax County was named.Today, Fort Belvoir is home to a number of important United States military organizations. With nearly twice as many workers as The Pentagon, Belvoir is the largest employer in Fairfax County. Fort Belvoir comprises three geographically distinct properties: the main base, Davison Army Airfield, and the Fort Belvoir North Area.