Fortifications

Fort Albany was a bastioned earthwork that the Union Army built in Arlington County (known at the time as Alexandria County) in Virginia. The Army constructed the fort during May 1861 as part of its Civil War defenses of Washington.

The fort had a perimeter of 429 yards and emplacements for 12 guns. Fort Richardson, Fort Craig and Fort Tillinghast provided supporting fire for the fort.

No trace of the fort remains, although a historic marker shows the location where the fort once stood, guarding the approach to the Long Bridge along the Columbia Turnpike, near the modern-day Pentagon.  ( Source - Wikipedia )