The US Navy had the five ships of the Washington class under construction but would like more ships in production. USS Washington had had to be scrapped, and the Lexington and Saratoga were converted to aircraft carriers, due to the effects of the Washington Naval Treaty. The twelve twin 16" turrets and the guns for them were warehoused for the chance that they could be used in the future or as replacements for the Colorado class. For the USA the need for those turrets and guns was now. 1938 and the Louisiana design is finalised. It will use the new Washington class arrangement with the twin turrets replacing the three triples.
Laid down in 1938, the Louisiana had a slightly different hull shape than the Washington class ships. Longer and narrower. A similar superstructure arrangement, but the extra length gave the opportunity to enlarge the machinery/ power plant, which with the finer hull, gave for a faster hull and overall speed increase. Being started slightly later than the Washington's, the Louisiana was designed with the 40mm Bofors guns in mind to be fitted, not the 1.1 inch mounting which had proved a failure in its short service career.
While the three ships were laid down almost a year later than the Washington class, the three ships were completed during the same timeframe due to the use of the already existing twin 16" weapons. All eight ships being completed in 1941-42. They were being received just at the time that the replacements for those battleships sunk at Pearl Harbour were required.