 The building of the first sixteen vessels was all authorised under the NIRA Executive Order on 16 June 1933; the last two were authorised under the Vinson-Trammell Act on 27 March 1934 (as part of a batch of 95 destroyers authorised on that date - covering DD-380 to DD-436 and DD-445 to DD-482). Contracts for the first six Mahans were awarded to three shipbuilders, but none of the builders had what the US Navy judged as an acceptable in-house design structure. On the strength of their reputation, the New York firm of Gibbs & Cox was named as the design agent. The firm had no experience in the design of warships, but had successfully designed passenger-cargo liners with better propulsion systems than any available to the US Navy. The decision was made to design the Mahan class and future classes around a new generation of machinery, including a cheaper, faster and more efficient propulsion system that combined increases in steam pressure and temperature with a new type of lightweight, fast-running turbine and double reduction gears.
