On August 18, 1863, as Beauregard and his staff sought to strengthen inner harbor defenses, Lieutenant Colonel D. B. Harris, Chief Engineer, was directed to construct a new battery for “heavy guns” at the site of the old mortar battery on Mount Pleasant. This fortification was placed to cover the Hog Island Channel, the inner harbor, and the bridge leading to Sullivan’s Island. The battery was armed with two 8-inch Columbiads on barbette carriages and designed to include a powder magazine.

On August 29, 1863, Thomas Jordan, Beauregard’s Chief of Staff, issued Special Orders No. 167, which named the new Mount Pleasant battery as Battery Gary in honor of Captain John Gary, commander of Company A, Lucas Artillery Battalion. Gary was killed on August 13, 1863, while serving at Battery Wagner on Morris Island.

A report in April 1864 confirmed the placement of two 8-inch Columbiads at Battery Gary and listed the ammunition inventory as 286 8-inch shells, 57 8-inch shot, eight 8-inch grapeshot, and twenty-eight 8-inch canister shot.

Battery Gary was located at the end of present-day Schweers Lane, adjacent to Pitt Street. The battery was constructed in the same area as a Revolutionary War Patriot fortification. The battery is destroyed and the property today serves as a private residence.