The Iowa class battleships were the final stage of dreadnought development for the United States Navy actually built; while technically the Montana class came afterward, none of those ships were ever laid down, much less completed. Funded in fiscal years 1940 and 1941, the Iowa class were the first battleships designed without regard for the restrictions of the Washington Naval Treaty, and so were larger (45,000 tons standard displacement), faster, and better armed than their predecessors of the South Dakota and North Carolina classes. Original funding called for six ships in the Iowa class, but only the Iowa, New Jersey, Wisconsin and Missouri were actually finished; the Illinois was cancelled in August 1945 and scrapped in 1958, while the Kentucky had its construction suspended several times before being launched in 1950 to clear the building dock. It too was scrapped in 1958.
Main armament for the Iowas consisted of nine 16-inch/50 caliber guns in three triple turrets, two forward and one aft. This was a slight improvement over the treaty battleships, whose main battery had nine 16"/45s. The secondary battery consisted of twenty 5"/38 caliber dual-purpose guns, and during World War II an additional eighty 40mm and 49 20mm anti-aircraft guns were carried. The original aircraft complement was three Vought OS2U Kingfisher seaplanes, replaced by Curtiss SC Seahawks later in the war. These seaplanes were replaced by helicopters starting with the Korean War, and during the Vietnam War, the New Jersey also carried QH-50 drones. The weapons mix for the battleships also changed over time; the New Jersey had its antiaircraft guns removed
for service in the Vietnam War, and the remaining Iowas had them removed when reactivated during the Reagan Administration. This reactivation also saw some of the 5"/38s removed to make room for Tomahawk cruise missiles, Phalanx defense systems, and Harpoon anti-ship missiles; in addition, an electronic warfare suite was added.
The Iowa and New Jersey were completed first, in early 1943, and spent World War II in the Pacific as part of carrier task forces, where their prodigious anti-aircraft weaponry helped screen the carriers from Japanese air attacks. The fast battleships were also used to bombard shore targets and as flagships for group commanders. Missouri and Wisconsin were not finished until 1945; Missouri is best known as the site of the Japanese surrender ceremony in Tokyo Bay later that year. All four battleships remained on active duty until the late 1950s, seeing action in Korea, but were placed in reserve with only the New Jersey reactivated for gunfire support in the Vietnam War. All four were reactivated and refitted as part of the rearmament program during the Reagan Administration in the 1980s, with Missouri and Wisconsin providing gunfire support during the first Gulf War, but were all decommissioned afterward as they were considered too expensive to maintain.
Today, all four Iowa class battleships have been stricken from the Naval Register; Iowa herself is in the "mothball fleet" at Suisun Bay, California, while New Jersey, Missouri, and Wisconsin have been donated to museums in Camden, Pearl Harbor, and Norfolk, Virginia respectively.