For thousands of years, horse racing flourished as the sport of kings and the nobility. Modern racing, however, exists primarily because it is a major venue for legalized gambling.
Horse racing is the second most widely attended U.S. spectator sport, after baseball.
Horse racing is also a major professional sport in Canada, Great Britain, Ireland, Western Europe, Australia, New Zealand, South Africa, and South America. By far the most popular form of the sport is the racing of mounted Thoroughbred horses over flat courses at distances from three-quarters of a mile to two miles. Other major forms of horse racing are harness racing, steeplechase racing, and Quarter Horse racing. By the time humans began to keep written records, horse racing was an organized sport in all major civilizations from Central Asia to the Mediterranean. Both chariot and mounted horse racing were events in the ancient Greek Olympics by 638 BC, and the sport became a public obsession in the Roman Empire.