American Flyer was a manufacturer of standard gauge and O gauge "tinplate" trains, based in Chicago, Illinois. It never produced S scale trains as an independent company. Chicago Flyer was purchased by A.C. Gilbert Co. in the late 1930s. Gilbert began manufacturing S scale trains around 1939 that ran on three rail "O" gauge track. This was known as 3/16" O gauge. Gilbert stopped producing trains during WWII. When the war ended, Gilbert began producing true S scale S gauge trains in 1946 under the American Flyer mark.