The most popular breed of racehorse is the thoroughbred, followed by the American quarter horse. Arabians and standardbreds are also used for racing in the United States.
Quarter horses are the most popular breed of horse in the United States, but most of them are not used for racing. However, the name is derived from their early popularity as a racehorse that excelled over short distances. Today, they are also popular in gymkhana races such as barrel racing and pole bending, which require the horse to gallop through a pattern.
Thoroughbreds, Arabians and quarter horses are generally raced on the flat and under saddle. Thoroughbreds are also used for steeplechasing, a type of race that requires the horses to jump over hurdles. Standardbreds are used for harness racing. They are classified as either pacers or trotters, depending on how they move.
Arabians are used for flat racing, but they also excel at endurance racing. This is a race that is run over long distances, typically 50 to 100 miles. The average pace is much slower than in shorter races so that the horses are able to go the entire distance. Any breed of horse can compete in endurance as long as the horse is sound and healthy. However, Arabians have been selectively bred for endurance, so most successful endurance horses are full or part Arabian.
There are also small racing meets for Appaloosas, American paint horses and mules.