U.S.S. Monitor was the first ironclad warship commissioned by the United States Navy during the American Civil War. She is most famous for her participation in the Battle of Hampton Roads on March 9, 1862, the first-ever battle fought between two ironclads. The Monitor fought the ironclad CSS Virginia (the former frigate USS Merrimack) of the Confederate States Navy. Monitor was innovative in several respects, including the first 360 degree rotating armored gun turret on an operational warship. The hull was completely underwater and was protected by an overhanging armored deck and armored “belt”. Her keel was laid on October 25, 1861, and she was launched 118 days later.