MCLEAN, Va. — Fort Marcy was completed in 1961 as a Union fortification on the northern bank of the Potomac River, whose batteries helped protect Leesburg Pike and the Chain Bridge, important entries into Washington, DC from Virginia. Located along the George Washington Memorial Parkway, the remains of the earthen works fort provide hiking trails around the fort and Civil War-era cannons within the earthen walls and dry moat of the fort.