Among early US aircraft builders were the brothers Oliver and William Thomas, who completed their first airplane during the winter months of 1910-11. This led to the formation of the Thomas Brothers Aeroplane Company in 1912. A number of designs were originated to meet the early requirements of the US Army. The growing capability of Thomas Brothers brought a merger with the Morse Chain Company to establish the Thomas-Morse Aircraft Corporation at Ithaca, New York, in January 1917.

In Europe, a major conflict had been raging since the summer of 1914, one which historians were later to label as World War I, but it was not until 6 April 1917 that the United States declared war on Germany. Ill-prepared to participate, the most urgent requirements of the Aviation Section of the US Army Signals Corps were aircraft, and trained pilots to fly them. Thomas Brothers had designed a single-seat scout, but after evaluation by the Aviation Section it was regarded as unsuitable for combat and was instead ordered from the Thomas-Morse company as an advanced trainer. Designated S-4B, initial procurement ran to 100 examples of these stagger-wing single-bay biplanes. They had a basic structure of wood with fabric covering, landing gear of tailskid type, and power provided by a 100-hp (75-kW) Gnome rotary engine (then being licence-built in the USA). The S-4C which followed had improved ailerons and aileron control system but only the first 50 of the 1,050 contracted retained the somewhat temperamental Gnome engine. The remainder had a Le Rhône rotary, but only 497 S-4Cs had been delivered at the time of the Armistice and the 553 then outstanding were cancelled. Ten examples of the S-4B and four of the S-4C were also acquired by the US Navy for use as advanced trainers.

Regarded as superior to the renowned Curtiss 'Jenny', S-4Cs soon found buyers when offered in the postwar surplus market. They saw much use until the late 1920s, when more stringent safety regulations brought their era to an end.