Dirt track racing is a type of auto racing performed on oval tracks. It began in the United States before World War I and became widespread during the 1920s and 30s. Two different types of racecars predominated—open wheel racers in the Northeast and West and stock cars in the South. While open wheel racecars are purpose-built racing vehicles, stock cars (also known as fendered cars) can be either purpose-built racecars or street vehicles that have been modified to varying degrees.