The Hunley was the first successful combat submarine, built in Mobile, Alabama and commissioned by the Confederate States of America during the American Civil War. It was used by the Confederacy against the Union blockade of Charleston, South Carolina. On February 17, 1864, the Hunley sank the Union sloop USS Housatonic and became the first submarine to sink an enemy warship, though the Hunley itself was lost at sea with its crew of 8 men. Nearly 140 years later, the Hunley was discovered and raised from the ocean floor, and has since undergone preservation and archaeological study to learn more about this pioneering submarine and the mystery of what exactly happened to its final crew.