Joe Hennissey was a sergeant with Company A of the Sixth U.S. Colored Heavy Artillery during the American Civil War. He was stationed at Fort Pillow in April, 1864. Just prior to the Battle of Fort Pillow, fellow sergeant Ben Robinson expressed concerns that the parapet of the fort was too thick to allow the heavy guns to be depressed low enough to aim at attackers who were close to the fort. Hennissey dismissed Robinson's concerns, primarily because the ship the USS New Era was anchored on the Mississippi River, ready to support the fort.