Blockhouse near Fort Haggerty on the Arlington Ridge Road, Virginia, helping guard the Aqueduct Bridge,...

Fort Haggerty was a small supplementary outwork of Fort Corcoran, constructed in May 1861 with a perimeter of 128 yards and emplacements for 4four guns, it was designed to bring under fire the slope south of Fort Corcoran, which could not be seen from therea supplementary defense to protect the Aqueduct Bridge leading across the Potomac River into Washington, DC. This blockhouse must have stood near the intersection of modern Wilson Boulevard at North Arlington Ridge Road in Arlington, Virginia, and was probably photographed early on a chilly spring morning in 1862 (when Barnard and Gibson are known to have been in partnership). This vView looking looks eastward over the Chesapeake & Ohio Canal and Potomac River toward the national capital; the dome of the Naval Observatory and incomplete Washington Monument are faintly visible in the far distance.