Few ships in American naval history have been so highly acclaimed as USS Monitor, a vessel that transformed naval warfare with its revolving turret. When Monitor, armed with only two cannons, fought the much more heavily armed CSS Virginia (constructed on the hull of USS Merrimac) to a draw on March 9, 1862, the world took note. In 1870 the British Admiralty built the turreted Captain. Decades later, in 1937, Winston Churchill wrote, 'The combat of the Merrimac and the Monitor made the greatest change in the sea-fighting since cannon fire by gunpowder had been mounted on ships about four hundred years before.'
The revolutionary Monitor nearly didn't get built. Controversy raged over engineer John Ericsson's design, and Abraham Lincoln had to intercede on behalf of the ship.