Fortifications

Fort Richardson was a detached redoubt that the Union Army constructed in September 1861 as part of the Civil War defenses of Washington. The Army built the fort shortly after its rout at the First Battle of Bull Run (Manassas) in late July 1861.[3] The Army named the fort after General Israel B. Richardson, whose division had been deployed to defend the City of Washington against attack by way of the Columbia Turnpike.

The structure, which was the highest fortification on the Arlington Line, occupied a commanding position on the crest of a ridge. It had a perimeter of 316 yards and emplacements for 15 guns, including a 100-pound Parrott rifle that could sweep a sector from Fort Ellsworth to Fort DeKalb (later named Fort Strong). The fort housed bomb-proofs and two ammunition magazines, and was adjacent to a military encampment.  ( Source - Wikipedia )