Montana Class Battleships

The Montana class of battleships were the last and largest class of battleships ordered by the US Navy, but work was cancelled before any of the five ships had even been laid down.

The previous Iowa class battleships were the first not to be restricted by any of the inter-war naval treaties, but they were restricted by the width of the lock gates in the Panama Canal. For the Montana class this last restriction was lifted, and instead new locks were ordered. This allowed the new ships to be 121ft wide, a 13ft increase on the width of the previous three classes.

The Iowa class ships had been designed as very fast battleships, capable of operating with the fast carrier force. The Montana class design reverted to earlier US tradition, where some speed was sacrificed in favour of armour and firepower. The Montana class ships had their armour improved to give protection against the new 2,700lb 16in shell that had been adopted by the US navy. On the South Dakota and Iowa class ships the armour had been sloped and had been built inside the anti-torpedo protection. On the Montana class of ships this idea was abandoned and instead they used external armour and a bulged form. This was believed to be easier to fit and to repair and to make the ships less vulnerable to flooding after damage to the belt. 

The extra space was also used to increase firepower. The Iowa class ships carried nine 16in/50 guns in three triple turrets, two forward and one aft. On the Montana class ships this would have been increased to twelve 16in guns in four turrets, two forward and two aft. Secondary firepower was also increased, with twenty 5in/54 guns carried in ten twin mountings. These guns provided more firepower against destroyers but had a lower rate of anti-aircraft fire.

Work on the Montana class ships was delayed in 1940 when the US decided to order two extra Iowa class ships (neither of which was completed). The five Montana ships and last two Iowa class ships were all authorised by the Two-Ocean Navy Bill of 1940. The five Montana ships were authorised under an Act of 19 July 1940, but none had been laid down when construction was suspended in April 1942 by Presidential direction. Work was suspended because of an apparent shortage of steel, which also caused the cancellation of the new Panama Canal locks. Work was finally cancelled on 21 July 1943. Not all of the work was wasted, as some features were used on the Midway class aircraft carriers, three of which were completed and saw useful post-war service. 

Displacement (standard)


Displacement (loaded)


Top Speed



15,000nm at 15kts

Armour – belt

16.1in-10.2in on 1in STS

 - internal belt


 - armour deck

6-7.35in with 2.25in deck and 0.62-0.75in splinter deck

 - bulkheads


 - barbettes


 - turrets

22.5in face, 9.15in roof, 10in side, 12 rear

 - CT

18in, 7.25in roof






Twelve 16in/50 guns in four triple turrets
Twenty 5in/54 guns in twin turrets
Thirty-two 50mm guns in quad mounts
Twenty 20mm guns
3 aircraft

Crew complement


Ships in Class

All cancelled 21 July 1943

USS Montana BB67


USS Ohio BB68


USS Maine BB69


USS New Hampshire BB70


USS Louisiana BB71


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How to cite this article: Rickard, J (10 October 2014), Montana Class Battleships ,

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