The Marsh Battery, also known as the “Swamp Angel,” was a Union battery constructed in 1863, strategically placed to fire shells directly into the city of Charleston. Armed with a 200-pound rifled and banded Parrott gun, the battery fired its first shot at 1:30 am on August 22, 1863. The large gun burst after its thirty-sixth shot.

The damaged gun is now placed in a monument in Cadwalader Park in Trenton, New Jersey. The Swamp Angel battery site is preserved by the South Carolina Battleground Preservation Trust through a permit issued in 1992 by the South Carolina Coastal Council. A simple sign marks the historic site in the marsh between Morris and James Islands.