Thoroughbred racehorses are a breed of horse known for their speed and endurance. Physical characteristics include an average height of 16 hands (64 inches or 62.56cm), a refined head, long neck, evenly curved back, and long, slender legs. They usually have bay, chestnut, black, or gray coats, and many have white markings on their face and legs. While Thoroughbreds are most widely known for their racing abilities, they have also proven to be quite adept at other sports such as hunting, jumping, and polo, and are frequently used to upgrade breeds of horses or to create entirely new breeds.
The ancestry of each thoroughbred can be traced back to three stallions - the Byerly Turk, Darley Arabian, and Godolphin Arabian - that were brought to England from the Middle East in the late 17th Century. They were then bred to native horses to create what is known as the Thoroughbred.
From the time this selective breeding process began, pedigree records have played an integral role in the Thoroughbred racing industry. Beginning with the General Stud Book, published by James Weatherby in 1791, and continuing with The Jockey Club, which is the breed registry for all thoroughbreds in North America, the names of over 3 million horses have been recorded and can be traced back to the late 1800s. With the advent of DNA typing, the Jockey Club is now able to verify parentage using mane hair, with a 99.9% accuracy rate, thereby enabling them to better maintain the quality and excellence of the Thoroughbred heritage. The Jockey Club also records the results of daily Thoroughbred races around the world.
Some notable Thoroughbreds of the 20th century include Man 'O War, who is considered by many to be the greatest American race horse of all time; Citation,the first Thoroughbred to earn $1 million over the course of his racing career; Native Dancer, affectionately known at the "Gray Ghost"; Secretariat, who set a world record by winning the Belmont Stakes with a 31-length victory; and Seattle Slew, the first undefeated Triple Crown winner.