A horse race is a contest in which horses are paired against one another and bettors place wagers on the outcome of the competition. In the United States, horse racing is a major industry and a popular spectator sport. In order to compete, a horse must be purebred. A thoroughbred is the most common breed for horse races, but other breeds may also be used. The rules of a horse race vary from country to country.

In the United States, horse racing is regulated by the state governments in which it takes place. State agencies may establish the number of races that must be run each year and impose restrictions on who can participate in the sport. In addition, most states have laws that require horses to be inspected by a veterinarian before they are allowed to compete.

Horses have long been an important part of human history. Historically, people have used them for transport, war, work, and entertainment. In the early days of the colonial era, there was great demand for horse power, and a number of race tracks were developed. A popular event was the steeplechase, a race over a series of obstacles — church steeples are traditional – that must be cleared by the participants. The steeplechase dates back to the 5th century bc, and it was described in detail by the Greek author Xenophon.

The earliest races in England were match contests between two or at most three horses. The pressure of public demand eventually led to events with larger fields of runners, and by the time organized racing began in America in 1664, the King’s Plate was a standardized race for six-year-olds over 4-mile (6.4-kilometer) heats. A win required winning both heats. As dash racing became the standard, the ability of a rider to gain a few feet gained in importance.

A jockey’s job is to guide a horse over a race course in the most efficient manner possible. A good rider will not interfere with the other horses in a race, and a horse that has a bad trip may have trouble gaining an advantage over its competitors. A rider’s skill is reflected in his or her ability to read the pace of a race and anticipate the moves of other riders. The clubhouse turn is the turning on a racetrack that is nearest the clubhouse. The term “closed knees” refers to the condition in which the cartilage that forms the knee joint on a horse is turned to bone. This is a sign of maturity. A horse with closed knees can move faster than a horse with open knees. The legs of a horse are called the front legs, and they are nicknamed the “pigeon toes” because they are so big and round. A clocker is an official whose duties include timing workouts and races. A jockey’s weight is measured by a clerk of scales before and after a race to ensure that the correct amount of weight is carried.