Fortifications

Fort Jackson (1861-1865) - A U.S. Civil War Fort first established in 1861 in Arlington County, Virginia. Named Fort Jackson after the area where the fort was situated.  This fort was also one of three forts built to protect the Long Bridge over the Potomac River from Virginia to Washington DC (Fort Albany, Fort Runyon and Fort Jackson). These forts were built early in the war and were the first line of defense for the Virginia end of the bridge. As the war progressed the line of defenses moved further south into Virginia and these forts became far less important and their garrisons were reduced. Fort Runyon and Fort Jackson were built on the road(s) to the bridge and Fort Albany was built later to protect the other two.

Fort Jackson was located on the Virginia end of the long bridge and the smallest of the three forts. It has been described as little more than "an outpost for pickets of a small force at the district end of the bridge". The post probably served as an inspection point for bridge traffic from the Virginia side and was probably not an armed site.  ( Source - Fortwiki )