USS Idaho, a 32,000-ton New Mexico class battleship, was built at Camden, New Jersey. Commissioned in March 1919, she steamed to Rio de Janeiro, Brazil, in July and then transited the Panama Canal to the Pacific, where she was based for the next dozen years. During that time, Idaho took part in the Battle Fleet's routine of drills and exercises, which extended from the Caribbean to Hawaii and as far south as Chile. She also cruised to Alaskan waters in 1920 and to New Zealand and Australia in 1925. In September 1931, the battleship entered the Norfolk Navy Yard for extensive reconstruction.
Emerging from the shipyard in October 1934, Idaho's appearance had been transformed. Gone were the "cage" masts that were such a distinguishing feature of American battleships of her era, now replaced with a tower superstructure supporting up-to-date gunfire controls. As one of the Battle Fleet's most modern units, Idaho returned to the Pacific in 1935 to again take up her peacetime work of preparing for possible combat.
With World War II raging in Europe, Idaho was transferred to the Atlantic Fleet in June 1941. Based in Iceland during much of the rest of that year, she helped cover convoys against the threat of German raiders during a period of "undeclared war". Following the devastating 7 December 1941 Japanese attack on Pearl Harbor, she was sent back to the Pacific, arriving in January 1942. For the next year, Idaho operated along the U.S. west coast and in the Hawaiian area. In April 1943, she went north to the Aleutians, where she supported the landings at Attu in May and Kiska in August.
Idaho next joined the drive across the Central Pacific, taking part in the Makin landing in November 1943, the Kwajalain invasion in February 1944, a bombardment of New Ireland in March, the Marianas operation in June and July, and the assault on the Palaus in September. Following an overhaul, she returned to the combat zone in time to provide heavy gunfire support for the February 1945 invasion of Iwo Jima. Idaho's 14" guns were again active bombarding Okinawa from late March into May 1945. While off Okinawa, she was damaged by a "Kamikaze" on 12 April, but returned to action after brief repairs.
The end of the Pacific War in August 1945 found Idaho preparing for the invasion of Japan. She was present in Tokyo Bay when Japan formally surrendered on 2 September, and shortly thereafter steamed back across the Pacific and through the Panama Canal, arriving at Norfolk, Virginia, in mid-October. Generally inactive from then on, USS Idaho was decommissioned in July 1946 and sold to a scrapper in November 1947.