The five battleships of the Montana class, authorized under the 1940 "Two Ocean Navy" building program and funded in Fiscal Year 1941, were the last of their kind ordered by the U.S. Navy. With an intended standard displacement of 60,500 tons, they were nearly a third larger than the preceding Iowa class, four of which were the final battleships actually completed by the United States. The Montanas were intended to carry twelve 16"/50 guns, three more than the earlier class. Protection against underwater weapons and shellfire was also greatly enhanced. They would have been the only new World War II era U.S. battleships to be adequately armored against guns of the same power as their own. To achieve these advances, the Montana class was designed for a slower maximum speed than the very fast Iowas and had a beam too wide to pass through the existing Panama Canal locks.

Preliminary design plans prepared for the General Board as part of the process leading to the Montana class (BB-67--71) battleship design. At the time, the Montana class was planned to begin with hull number BB-65, rather than BB-67 as it became after two more Iowas were ordered as BB-65 and BB-66. None of these plans represent the design finally adopted for the Montana class.

The Battleship Study - BB65 - Scheme 3 - (1940 Studies), dated 6 February 1940, was for a ship of 52,500 tons standard displacement and 64,500 ton trial displacement, with a main battery of twelve 16"/50 guns, a secondary battery of twenty 5"/38 guns and a 130,000 horsepower powerplant for a speed of 28 knots. Ship's dimensions are: waterline length 860'; waterline beam 114'; draft 36'. Scale of the original drawing is 1/32" = 1'. Port side 5" gun arrangement is labeled "previous secondary battery arrangement". Starboard side has a "proposed secondary battery arrangement."

The "Battleship Study - BB65 - Scheme 4 - (1940 Studies), dated 14 February 1940, was for a ship of 54,500 tons standard displacement and 64,500 tons trial displacement, with a main battery of twelve 16"/50 guns, a secondary battery of twenty 5"/54 guns and a 150,000 horsepower powerplant for a speed of 28 knots. Ship's dimensions are: waterline length 870'; waterline beam 114'; draft 36'. Scale of the original drawing is 1/32" = 1'.

The "Battleship Study - BB65 - Scheme 8 - (1940 Studies), dated 15 March 1940, was for a ship of 70,000 tons standard displacement and 82,000 ton trial displacement, with a main battery of twelve 16"/50 guns, a secondary battery of twenty 5"/54 guns and a 320,000 horsepower powerplant for a speed of 33 knots. Ship's dimensions are: waterline length 1050'; waterline beam 120'; draft 35'. Scale of the original drawing is 1/32" = 1'.

The year 1940 also saw the beginning of another project, which, like the transisthmian highway, had been "in the cards" for some time past. Concern over the possibility that the Canal might be put out of operation by sabotage or aerial attack against the lock system had on various occasions given rise to proposals to construct another canal either in Nicaragua or across the Isthmus of Tehuantepec, to convert the Panama Canal into a sea-level waterway, or to build an additional set of locks. Of these several proposals, the War Department favored the third on grounds that it would be the quickest and least expensive, and that in any case it would be a prerequisite for building a sea-level canal.

Construction and planning were placed in the hands of the Canal administration, not of the Army, although the War Department controlled the purse strings. The plans called for a series of single locks paralleling, but at some distance from, the existing double chambers. The new locks were to be two hundred feet longer and thirty feet wider than the old, in order to accommodate the 58,000-ton Montana-class battleships that the Navy placed on order in September 1940. This feature soon began to override the security consideration as the principal reason for the project.

Completion of the Montana class would have given the late 1940s U.S. Navy a total of seventeen new battleships, a considerable advantage over any other nation, or probable combination of nations. The Montanas also would have been the only American ships to come close to equalling the massive Japanese Yamato. However, World War II's urgent requirements for more aircraft carriers, amphibious and anti-submarine vessels resulted in suspension of the Montanas in May 1942, before any of their keels had been laid. In July 1943, when it was clear that the battleship was no longer the dominant element of sea power, their construction was cancelled.