These were (I think) rail racers, promoted as a spectator sport, powered by model airplane engines. If you look closely at the car on the lower left corner, what looks like a radio antenna sticking up is the shut-off for the ignition system. As BiffRayRock noted, WWII killed this version of the hobby, but it was resurrected immediately postwar in tether car ("Spindizzy") format. The greatest makers were the Dooling Brothers, whose location was listed as:
3433 West 59th Street
5452 West Adams Boulevard
Los Angeles 16, California
The Dooling .61 was the Offenhauser of model engines. One in good condition will set you back about 2500 bucks and their cars go for four grand or so.
Cheers,
Earl