The New Mexico-class battleships of the United States Navy, all three of whose construction began in 1915, were improvements on the design introduced three years earlier with the Nevada class. The twelve-gun main battery of the preceding Pennsylvania class was retained, but with longer 50 caliber guns in improved triple turrets. Hull design was also upgraded with a 'clipper' bow for better seakeeping and a sleeker look. One ship, the New Mexico, was fitted with turbo-electric propulsion.