Fort Ethan Allen was built in September 1861 by 2nd Vermont Volunteer Infantrymen and named for Ethan Allen, a Revolutionary War hero from their state. In northern Virginia, it shared features with other Defenses of Washington forts and, with a perimeter of 768 yards, was one of the earliest, largest, and most heavily armed. Its construction followed the directives of General John G. Barnard, chief engineer for the U.S. Army Corps of Engineers. The fort included ground-level entrances cut through raised parapets and ramparts and facing away from exposed fronts, a guard house near the front entrance with offices, a room for prisoners, and space for mustering guards, underground powder magazines and filling rooms for ammunition, black powder, projectiles, shells, and cannon-firing implements, bombproofs near the center for protection from artillery fire, and a covered way that concealed soldiers moving to defensive positions outside the walls. During the war, the surrounding area was cleared of trees, orchards, and farms to make way for forts, rifle trenches, and military roads. After the war, the fort was ordered closed, and at public auction the U.S. Army sold all salvageable materials and tools. Legend holds that lumber from the fort was used to build the house at 3111 North Glebe Road, known as Bellevue.