In the 1890s, three pairs of large 10-inch caliber disappearing guns formed a key part of the river defense system, with each weapon able to fire a 650-pound projectile at enemy ships within a seven-mile range. Battery Humphries is one of three similar structures at Fort Washington Park. Fort Washington is the site of the first permanent fort built between 1814 and 1824 to guard the Potomac River approach to the Nation's Capital.