Which was the first American fighter designed from scratch to naval specifications?

In 1921, while working at the Bureau of Aeronautics, Rex Beisel designed the TS-1, the first US Navy fighter actually built to naval specifications. Beisel had entered that world in 1917 as a draftsman, earning $4 a day, and became fascinated with aviation there. His first jobs involved hulls, wing floats, and pontoons for seaplanes. He showed such skill at that work that he soon began receiving promotions.

In 1923, the Curtiss Aeroplane and Motor Company drew him into the private sector and named him chief engineer at age 29. Two years later, aircraft of his design won first and second place in the prestigious Pulitzer Trophy races. After a brief stint at Spartan Aircraft, Beisel became assistant chief engineer at Chance Vought in 1931.

In 1926, the Navy awarded Vought a $459,709 contract for twenty convertible land-and-sea fighters. That aircraft, redesignated the FU-1, reached 147 mph (237 km/h) at 13,000 ft (4,000 m) with the help of its supercharger.