The South Dakota-class was a group of four fast battleships built by the United States Navy. They were the second class of battleships to be named after the 40th State; the first class was designed in the 1920s and canceled under the terms of the Washington Naval Treaty. The class comprised four ships: South Dakota, Indiana, Massachusetts, and Alabama. They were more compact and better protected than the preceding North Carolina class, but had the same main battery, nine 16-inch (406 mm)/45-caliber guns in triple turrets. The ships can be visually distinguished from the earlier vessels by their single funnel, compared to twin funnels in the North Carolinas. According to authors William Garzke and Robert Dulin, the South Dakota design was the best "treaty battleship" ever built.