Fort Palmetto was a three-gun battery built at the eastern terminus of the Christ Church Lines, where it commanded both Copahee Sound and Dewees Inlet, a possible access point for Federal ships entering from the ocean between Long Island (Isle of Palms) and Dewees Island. Because Dewees Inlet was twelve feet deep at mean high tide and seven feet deep at low tide, it had enough water for a light-draft ship or barge carrying troops. As early as the fall of 1861, the Federal navy was exploring the waterways from Charleston to McClellanville, and Christ Church Parish, east of the Cooper River, was recognized by the Confederate army in Charleston as a potential point of attack during the Siege of Charleston. The Christ Church Lines were built to defend the parish from an infantry attack coming from the northeast, and Fort Palmetto was strategically placed to stop Federal ships trying to advance on Charleston by the inland waterways. The earthwork fortification measured 160 feet long and eighty feet deep, with a parapet fifteen feet tall, a powder magazine twenty-five feet tall, and a second powder magazine or bombproof. A company of the 20th South Carolina Volunteer Infantry served as the garrison for much of the war. The fort was armed with one 9-inch Dahlgren gun and two 32-pound rifled and banded guns; the Dahlgren had an effective range sufficient to fire on the inland waterway less than two miles from the fort, while the two 32-pound guns had a much longer range that could reach Dewees Inlet, a little more than four miles away. These guns became an effective deterrent to the many Union ships, large and small, that probed the inland waterways.