Fort Palmetto, a three-gun battery, was constructed at the eastern terminus of the Christ Church Lines. This strong fortification commanded both Hamlin Sound and Dewee’s Inlet. Dewee’s Inlet, located between Long Island (Isle of Palms) and Dewee’s Island, was a possible access point for Federal ships coming in from the ocean. The inlet was twelve feet deep at mean high tide and seven feet deep at low tide, enough water for a light-draft ship or barge transporting troops.

The earthwork fortification measured 160 feet long and eighty feet deep with a parapet fifteen feet tall and included a powder magazine twenty-five feet tall. It was armed with one 9-inch Dahlgren gun and two 32-pound rifled and banded guns. A company of the 20th South Carolina Volunteer Infantry served as the garrison for much of the war.