Fort Ethan Allen was constructed during the Civil War as one of the last lines of defense against possible Confederate attacks aimed at Washington, commanding the approaches to Chain Bridge over the Potomac River from south of Pimmit Run. Built by troops from Vermont in 1861 and named for Ethan Allen, Vermont's famous Revolutionary War commander, it was a large earthwork garrisoned by as many as 1,000 men, with a perimeter of 736 yards and emplacements for 36 guns. Its armament included three 6-pounder guns, four 24-pounder guns, three 32-pounder guns, two 8-inch howitzers, three 32-pounder howitzers, three 10-pounder Parrotts, eleven 30-pounder Parrotts, six 12-pounder Napoleon guns, four 10-inch mortars, and two 24-pounder Coehorn mortars. Military Road linked it with Fort C.F. Smith to the south. The nearest fighting occurred on July 11-12, 1864, at Fort Stevens, six miles to the northeast. Segments of the south face, gun platforms, one bombproof, traces of a stone magazine, and a guardhouse still can be identified, and a portion of the original rifle trench can be seen at the south end of Fort Ethan Allen Park adjacent to Glebe Road Park. The officers' quarters, barracks, cookhouses, and mess houses, none of which remain, were located to the east of the fort.
