From Wikipedia http://en.wikipedia.org/wiki/Charleston_Arsenal
"The Charleston Arsenal was a United States Army arsenal facility in Charleston, South Carolina seized by state militia at the outbreak of the American Civil War.
With the secession of South Carolina in late 1860, it became a target for Confederate sympathizers and local militia. South Carolina troops seized the arsenal in late December, and the Confederates held it for much of the war. Josiah Gorgas had the arsenal enlarged and modernized with the installation of steam power. For a time, it was used a barracks to house Confederate troops, including the 26th South Carolina. The arsenal was finally retaken by Union troops in 1865 when Charleston finally fell."