Fort Lesley J. McNair is a United States Army post located on the tip of Greenleaf Point, the peninsula that lies at the confluence of the Potomac River and the Anacostia River in Washington, D.C. To the peninsula's west is the Washington Channel, while the Anacostia River is on its south side. Originally named Washington Arsenal, the fort has been an army post for more than 200 years, third in length of service, after the United States Military Academy at West Point and the Carlisle Barracks.