Thoroughbreds are the fastest horses around. All thoroughbreds are descendant of three stallions imported to England in the 17th century—the Darley Arabian, the Godolphin Arabian, and the Byerly Turk. These stallions were bred with English mares to create a hardy racing horse. Thoroughbreds can be bay, brown, chestnut, black, or gray in color. Organized thoroughbred racing in America started in the mid-18th century. Since then it has become a major sport—the English Jockey Club estimates that anywhere between 30,000 and 40,000 foals are registered every year. Thoroughbreds are massive animals—they can weigh more than 1,000 pounds and run as fast as forty miles per hour.