Spotted or sorrel, Quarter horses speed past. Nicknamed 'America's Horse,' the Quarter horse is an excellent sprinter. Actually, that's how the Quarter horse got its name-many of the races that this breed won were a quarter mile or less. Working during the week and racing on the weekend, this breed found widespread approval in colonial America. As the most popular breed in the fifty states, the Quarter horse breed is also the largest breed registered in the world. Not just a racer, Quarter horses are also found in arenas of rodeos, ranches, and shows.