The first USS Louisiana (BB-19) was a vessel of no great note. Commissioned in 1906, Louisiana was one of the last pre-dreadnought battleships. The completion of the British Dreadnought in 1907 rendered Louisiana and her ilk obsolete. Nevertheless, Louisiana served in Theodore Roosevelt’s Great White Fleet, and patrolled near Mexico during the disturbances of the Revolution. Louisiana was decommissioned in 1920 and scrapped in 1923.
The second USS Louisiana (BB-71) would have been a ship of somewhat greater import. Louisiana was to be the fifth ship of the Montana class, a group of battleships designed specifically to fight the Japanese Yamato. Louisiana was designed to displace 60000 tons, carry 12 16″ guns, and make 28 knots. If built, Louisiana and her sisters would have been the most powerful battleships in the world. Contrary to popular opinion, the Yamato class battleships would likely not have fared well against the US Iowa class. The Iowas had better fire control, better damage control, more speed, better designed armor, and better underwater protection. The 16″ guns of the Iowa had greater penetrating power than the 18″ guns of Yamato, and a rate of fire nearly twice as high. The Louisiana design multiplied these advantages, and likely would have made short work of Yamato.
Sadly for battleship enthusiasts, the aircraft carrier made such comparisons pointless. Swarms of carrier aircraft sank Yamato and Musashi before they could meet the best battleships of the USN. Louisiana was cancelled in early 1943, before the laying of the keel. Even if begun, it is unlikely that the ship would have been completed.