Fort Sumner was built during the American Civil War by the Union Army in the Brookmont section of Bethesda, Maryland, just northwest of Washington, D.C.

The fort had a commanding view above the Potomac River and included 30 artillery pieces.

[3] Battery Bailey was named for Captain Guilford D. Bailey, killed in action at the Battle of Fair Oaks, and Battery Benson was named for Captain Henry Benson, mortally wounded in action at the second engagement at Malvern Hill.

[5] There are a few visible remains of Battery Bailey in Westmoreland Hills Park, which can be seen from the adjacent Capital Crescent Trail.

[3] Part of the site was acquired by the Army Map Service (AMS) early in World War II and renamed Fort Sumner.