A third structure, called the South Battery or Half-Moon Battery, is located at the southeast corner of the original island near Buttermilk Channel, and was built before the War of 1812. The arrowhead-shaped South Battery contained 13 barbette guns, mounted on the parapet and facing Buttermilk Channel, as well as a barracks inside. It was then used as an officer's mess and Catholic chapel by 1878; as a court-martial room by the 1880s; and as an amusement hall after a 1904 renovation. From the 1930s, South Battery was also used as an officers' club.