Capital Defense – Washington, D.C., in the Civil War
By Marc Leepson
8/26/2009 • America's Civil War
When the first inklings emerged early in 1861 that a fighting war pitting North versus South would soon break out, the residents of Washington, D.C.—at least those whose sympathies were with the Union—began to feel more than a little threatened. Though it was a haven for freed blacks, the District of Columbia also was the home of slave-owning whites and had the ambience of a Southern city, sitting below the Mason-Dixon line and surrounded by the slave-owning states of Maryland and Virginia.
The city’s only defensive fortification was Fort Washington, built in 1809 well south of the city on the Maryland side of the Potomac River. Worse, only a handful of friendly troops were stationed nearby, and many of them defected to the Confederate side.
http://www.historynet.com/capital-defense-washington-dc-in-the-civil-war.htm
