Fort Greble was an American Civil War-era Union fortification constructed as part of the defenses of Washington, D.C. during that war. Named for First Lieutenant John Trout Greble, the first West Point graduate killed in the U.S. Civil War, it protected the junction of the Anacostia and Potomac rivers, and from its position on a bluff in the Congress Heights, precluded any bombardment of the Washington Navy Yard and southeastern portions of the city. It was supported by Fort Carroll to the northeast and Fort Foote to the south. It never fired a shot during the war, and after a brief stint as a U.S. Army Signal Corps training facility, was abandoned and the land returned to its natural state.