Societe des Moteurs Le Rhone of Paris began manufacturing air cooled rotary engines in 1910. Its rotary was sufficiently different than that first developed by the highly successful Seguin brothers of the Societe des Moteurs Gnome, also of Paris, that it circumvented relevant Gnome patents; but was taken over by Gnome in 1914. Because Le Rhone products were in some ways superior to Gnome, its design engineers were permitted to continue development during World War I, resulting in large scale production of various nine cylinder engines.
During the World War I era, this engine was also produced in the United States by the Union Switch and Signal Company. Used mainly on fighter aircraft where speed and maneuverability were especially important, rotary engines were light and compact for their power. The Le Rhone Model 9C was used on Nieuport, Ruchonnet, Hanriot, Bleriot-SPAD, Morane, Sopwith, Farman, Caudron, and Voisin I aircraft.