The three Maine-classbattleships: Maine, Missouri, and Ohio were launched in the first several years of the 20th century. These were the first US capital ships to use smokeless powder for their main batteries, and the last to use Harvey armor. Smokeless powder allowed a decrease in gun size, with an increase in power and efficiency. Harvey armor, though only in use for a decade, was already obsolete. This was also the first US battleship class to use submerged torpedo tubes; this became possible because the hulls were at least 20 feet longer than previous US battleships.
The Maine-class of three battleships was authorized by Congress on 4 May 1898, 8 days after the start of the Spanish–American War.[page needed] The original plans called for an improved version of USS Iowa, which had been authorized in 1892. The main batteries were to be increased from 12-inch to 13-inch guns and the 4-inch guns with 5-inch guns.[page needed]
However, the original design was modified by chief engineer George W. Melville to add new technologies. The planned 13-inch 35 caliber guns were replaced by a smaller but more powerful 12-inch 40 caliber gun, which used the new and more efficient smokeless powder. The new design also specified Krupp cemented armour which would allow the thickness of the belt armor to be reduced from 16.5 to 12 inches.[page needed]
Further modifications were approved by the Navy Department on 8 October 1898, including adding two more 6 inch/50 caliber guns, moving torpedo tubes from above-water to submerged locations, and dropping the Krupp Cemented armor, returning to the original design with Harvey armor.[page needed] Some proposed changes were denied including, additions to the secondary batteries and William Cramp and Sons' offer to expand the ships by 15 feet to accommodate more powerful Niclausse boilers. The latter would have increased the speed to 18 knots.