Montana class (1940)
The 16" (406mm) gun was by no means uniquely American, but the US Navy favored it more than most. After the end of the Washington Treaty ban on battleship construction, the US built battleships armed exclusively with 16" main batteries. After the 35,000 ton designs of the North Carolina and South Dakota classes, the USN knew something was up with the German and Japanese battleship construction, and suspected that they were going over the Treaty limit of 35,000 tons. As a result, the following Iowa-class received a 10,000 ton displacement limit boost. When this was deemed too small, the Montana-class was designed. Previously, the US had restricted warship construction to sizes that would allow the ships to pass through the Panama Canal, since they needed to operate in two oceans. The Montanas were designed without this restriction, and would subsequently have been too large to pass through. Displacing 64,240 tons (nearly 20,000 more than the Iowas), and with a length of 921 feet (280.8m) , the Montana class would have dwarfed their cousins. However, their top speed was reduced to 28 knots, seven below the Iowas. The 16"/50 caliber Mk. 7 gun was retained, but a fourth turret was added, making the total gun count twelve. Congress approved the construction of the five Montanas in the Two-Ocean Navy Act of 1940, and provided the funds the following year. The ships were officially ordered in May, 1942, but were suspended later that month. The whole class was cancelled in July, 1943, with no keel having been laid.