Fort Lesley J. McNair is a United States Army post located on the tip of a peninsula (Greenleaf Point) that lies at the confluence of the Potomac River and the Anacostia River in Washington, D.C. To its west is the Washington Channel, while the Anacostia River is on its south side. It has been an Army post for more than 200 years, third only to West Point and Carlisle Barracks in length of service.
The military reservation was established in 1791 on about 28 acres (110,000 m2) at the tip of Greenleaf Point. Maj. Pierre (Peter) Charles L'Enfant included it in his plans for Washington, the Federal City, as a major site for the defense of the capital.
An arsenal first occupied the site and defenses were built in 1794. The fortifications did not halt the invading British in 1814. Soldiers at the arsenal evacuated north with as much gun powder as they could carry, hiding the rest in a well as the Redcoats came up the Potomac from burning the capitol. About 47 British soldiers found the powder magazines they'd come to destroy empty. Someone threw a match into the well and "a tremendous explosion ensued," a doctor at the scene reported, "whereby the officers and about 30 of the men were killed and the rest most shockingly mangled." The remaining soldiers destroyed the arsenal buildings, but the facilities were rebuilt after the war.