 Complete the following phrase:  Fort Jackson was an American Civil War-era fortification in Virginia that defended the southern end of the Long Bridge, near Washington, D.C. Long Bridge connected Washington, D.C. to Northern Virginia and served as a vital transportation artery for the Union Army during the war. Fort Jackson was named for Jackson City, a seedy suburb of Washington that had been established on the south side of the Long Bridge in 1835. It was built in the days immediately following the Union Armys occupation of Northern Virginia in May 1861. The fort was initially armed with four cannon used to protect the bridge, but these were removed after the completion of the Arlington Line, a line of defenses built to the south. After 1862, the fort lacked weapons except for small arms and consisted of a wooden palisade backed by earthworks. Two cannon were restored to the fort in 1864 following the 