South Dakota-class battleship (1920)

Model of the South Dakota-class battleship
Class overview
Name:	South Dakota class
Builders:	New York Naval Shipyard Mare Island Naval Shipyard Norfolk Naval Shipyard Newport News Shipbuilding Bethlehem Shipbuilding Corporation
Operators:	United States Navy
Preceded by:	Colorado class
Succeeded by:	North Carolina class
Cost:	$21,000,000 (cost limit)
Planned:	6
Cancelled:	6
Preserved:	0
General characteristics
Type:	Battleship
Displacement:	Standard: 41,400 long tons (42,100 t) Design: 43,200 long tons (43,900 t) Full: 47,000 long tons (47,800 t)
Length:	684 ft (208 m) overall 660 ft (200 m) waterline
Beam:	106 ft (32 m)
Draft:	33 ft (10 m) (design)
Installed power:	12 × boilers, 60,000 hp (45,000 kW) (South Dakota, Indiana, Iowa: White-Forster) (Montana, North Carolina: Bureau express) (Massachusetts: Yarrow)
Propulsion:	4 × Westinghouse steam turbine electric drives (BB−49–BB−52) 4 × General Electric steam turbine electric drives (BB−53–BB−54) 4 × propeller shafts
Speed:	23 knots (43 km/h)
Range:	8,000 nautical miles (15,000 km; 9,200 mi) at 10 knots (19 km/h; 12 mph)
Complement:	137 officers, 1404 enlisted, 75 marines
Armament:	12 × 16"/50 caliber Mark 2 guns (4×3) 16 × 6"/53 caliber Mark 13 guns 4 × 3"/50 caliber guns (dual purpose) 4 × 6-pounder Hotchkiss (saluting guns) 2 × 21-inch submerged torpedo tubes
Armor:	Belt: 8–13.5 in (203–343 mm) Barbettes: 4.5–13.5 in (114–343 mm) Turret face: 18 in (457 mm) Turret sides: 9–10 in (229–254 mm) Turret top: 5 in (127 mm) Turret rear 9 in (229 mm) Conning tower: 8–16 in (203–406 mm) Decks: 3.5–6 in (89–152 mm) Bulkheads: 8–13.5 in (203–343 mm) Uptakes: 9–13.5 in (229–343 mm) Secondary armament: none

684 ft (208 m) overall

The first South Dakota class was a class of six American battleships that were laid down in 1920 but never completed. They would have been the last dreadnoughts in the Naval Act of 1916 to be commissioned had the Washington Naval Treaty not caused their cancellation one-third of the way through their construction. They would have been the largest, most heavily armed and armored battleships in the U.S. Navy and, designed to achieve 23 knots (43 km/h), represented an attempt to abandon its 21-knot (39 km/h) standardized fleet speed and catch up with the increasing fleet speeds of its main rivals, the British Royal Navy and Imperial Japanese Navy. In this, size and secondary armament, they represented a break from the Standard-type battleship that had dominated American capital ship design for the prior five ship classes, while their use of standardized bridges, lattice masts and other features was a continuation of this practice and the increase in the number of main guns from the preceding Colorado class had long been standard U.S. naval policy. The main restriction to which they had to adhere was the ability to pass through the Panama Canal.

The South Dakotas were authorized 4 March 1917, but work was postponed so that the U.S. Navy could incorporate information gained from the Battle of Jutland, fought in 1916, in this class's final design. Work was further postponed to give destroyers and other small fighting vessels priority as they were needed urgently to fight German U-boats in the North Atlantic. Construction started only in 1920. As the Washington Naval Treaty both restricted the total allowable battleship tonnage allowed the U.S. Navy, and limited individual ship size to 35,000 tons, construction was halted 8 February 1922. While the unfinished hulls (most over 30% completed) were scrapped in 1923, the armor plates already prepared were left unused in the shipyards until World War II. The 40- and 50-ton plates intended for Montana, for instance, were sent in 1941 or 42 to the Panama Canal to reinforce the defenses and locks there. The 16" guns were transferred to the U.S. Army for use in coastal artillery.