USAC

USAC, or the United States Automobile Club, is a racing organization that has run since 1956. It was created at that time to take over for the American Automobile Association (AAA), which stopped sponsoring auto racing after the Le Mans disaster of 1955.

From 1956 until 1979, USAC was responsible for running the highest level championship in American open-wheel racing. At that time, a number of car owners unsatisified by USAC's running of the championship broke away to form CART (now ChampCar), which would easily replace USAC as the elite open-wheel format in the U.S. USAC however, was still responsible for running the Indianapolis 500, although CART did include the event in its schedule and points standings.

USAC's involvement in the 500 came to an end in 1997, when the event shifted into the hands of the Indy Racing League (IRL). USAC still exists in running sprint and midget car events that have been the springboards to higher levels for many American drivers, like Tony Stewart and Jeff Gordon.