The Battleships of the Nevada and Pennsylvania classes had established American ship design as second to none in 1916. At the same time the US Navy was planning advances in engineering systems that would change naval engineering forever.
The ships of the New Mexico class were improvements on the preceding Nevada and Pennsylvania class half sisters. Their hull was lengthened and beam increased. Additionally the new class was given a clipper bow to improve sea keeping capabilities. While they maintained the same main battery layout of four turrets mounting three 14” guns each, however the guns were a higher caliber 14”/50 models that would also be mounted on the California class. The New Mexico was also the test bed for a new power plant which featured General Electric geared turbines with electric drive which would be standard on succeeding classes of battleships as well as carriers, cruisers and destroyers. The Mississippi and Idaho retained the older geared turbine design. The practical effect was that the New Mexico required less horsepower to attain the same speeds as the earlier design turbines.
Displacing 32,000 tons the ships were slightly larger than their predecessors. New Mexico was launched on 23 April 1917 and commissioned on May 18th 1918. Her sisters Mississippi and Idaho were actually launched and commissioned sooner being launched on January 25th 1917 and commissioned on December 18th 1917. None of the ships saw action in the First World War and in 1919 the three would become the nucleus of the newly formed Pacific Fleet. They would serve in the Pacific but conduct exercises with the Atlantic Fleet in the Pacific as well as the Atlantic and Caribbean. All three were modernized in the early 1930s receiving improvements in armor protection, anti-torpedo blisters, a modernized bridge structure to replace their cage masts, improvements to machinery and their secondary armament.
They would return to the Pacific but with the outbreak of war in Europe the three ships were transferred to the Atlantic Fleet where they took part in the Neutrality Patrol. When Pearl Harbor was attacked the three sisters went back to the Pacific where they spent much of 1942 escorting convoys and being prepared to repel any Japanese assault on the US Mainland. In April 1943 they took part in the Aleutian campaign and the assaults on Attu and Kiska. They would then sail to the Central Pacific where the provided support to the invasions of the Gilberts, Marshalls and Marianas islands by protecting the transports and providing naval gunfire support to Marines ashore.
The three would again operate together during the invasion of the Philippines where the Mississippi served with other battleships of the 7th Fleet’s battle line under Rear Admiral Jesse Oldenforf at the Battle of Surigo Strait where they annihilated a Japanese force including the battleships Fuso and Yamisharo. Both Mississippi and New Mexico were damaged by Kamikaze hits in Philippine waters, the New Mexico taking a hit on her bridge which killed her Captain and 27 crewmembers. Both would require repairs and both would miss the invasion of Iwo Jima which Idaho took part in. The three joined forces again at Okinawa where they provided fire support to Marines and Soldiers ashore. They would serve until the end of the war in the Pacific and take part in Operation Magic Carpet to return military personnel from the Pacific to the United States.
Following the war the New Mexico and Idaho were decommissioned and sold for scrap in 1948. Mississippi however was converted into a gunnery training ship and reclassified as AG-128.
In this capacity she served as a test bed for new weapons including the Terrier guided missile systems which would be mounted on the first generation of US Navy Guided Missile Cruisers. She was decommissioned in 1956 and sold for scrap after an abortive attempt by the state of Mississippi to acquire her as a memorial ship.
The ships provided valuable service during the Second World War and the technical innovations in propulsion and protection would become standard in subsequent classes of US Navy battleships. Additionally the post war service of the Mississippi helped propel the Navy into the missile era helping to build a foundation that is in evidence today in the Ticonderoga Class Guided Missile Cruisers and Arleigh Burke class Guided Missile Destroyers and their Aegis air defense and ballistic missile defense systems. The ships of the New Mexico class and their stalwart crews should not be forgotten.