The AMA Supercross Championship is an American motorcycle racing series. The race series was founded and sanctioned by the American Motorcyclist Association (AMA) in 1974. Supercross is an offshoot of the sport of motocross which is held on natural terrain, closed courses. Supercross racing involves off-road motorcycles on an artificial, man-made dirt track consisting of steep jumps and obstacles. The AMA Supercross Championship is sponsored by Monster Energy and is held from January through early May in major league baseball and football stadiums. The easy accessibility and comfort of these stadium venues meant that by the late 1970s, Supercross had surpassed motocross as a spectator attraction in the United States.