The American Motorcyclist Association Supercross is a league of off-road motorcycle racers that compete against each other on off-road or dirt tracks. The tracks have many turns and hills that frequently send the competitors airborne during the race.
The AMA established the National Championship Motocross Series in 1972, and the first official Supercross races took place in 1974. The Supercross season begins in January and ends in May. Each event has two race classes with a 450cc class race in every event and either a 250cc East or 250cc West race. The final event of the Supercross season includes three races, one for each class.