Colorado-class battleship

The Colorado class was a group of United States Navy battleships, the last American battleships designed and built before the Washington Naval Treaty and the last with main guns in four twin turrets. Four were laid down, but only Colorado, Maryland and West Virginia entered service; Washington was launched and then cancelled under the treaty. They were improved Tennessee-class ships that traded twelve 14-inch guns for eight 16-inch guns, which made Maryland the most powerful battleship in the world when she was new in 1921. Their machinery was unusual: oil-burning boilers fed General Electric turbines that drove generators, and the generators sent current to electric motors on the propeller shafts. Newport News Shipbuilding laid down Maryland in April 1917 and West Virginia in April 1920, while New York Shipbuilding built Colorado and Washington. Maryland and West Virginia were at Pearl Harbor in December 1941, and West Virginia was sunk there, then raised and rebuilt. The three completed ships were scrapped by the late 1950s.