A horse race is a contest between two or more horses that are either ridden by jockeys or pulled by drivers in sulkies. The winner is declared by a photograph taken at the end of the race and studied by a panel of stewards to determine who finished first. Although horse races may differ slightly between national horse racing organizations, most use the same basic rules.

In the early years of the sport, most horse races were match races where an owner provided a purse and bettors placed a wager on each competitor. Those who withdrew forfeited a share of the stakes, and agreements were recorded by disinterested third parties known as keepers of the match book.

By the 1750s, six-year-olds and older were able to compete in King’s Plates, a series of standardized four-mile heats in which a horse had to win two races to be declared the winner. The races continued until the 1860s.

As horses became faster and more powerful, the sport evolved into one in which the winner was determined by a photograph taken at the finish line and studied by a panel of stewards who decided who won. This method of determining a winner was more precise than the previous system in which a horse had to be physically present at the finish line to be considered for a race.

The photo finish system has not been without its critics, however. It has been criticized for allowing owners to manipulate the results of a race. In addition, the process is difficult to verify. As a result, some horse owners have used the system to cheat and even kill competitors.

There are three kinds of people in horse racing, according to Patrick Battuello, who runs the activist group Horseracing Wrongs: the crooks who dangerously drug and otherwise abuse their horses; dupes who labor under the fantasy that horse racing is broadly fair and honest; and masses of honorable souls who know that the industry is more crooked than it ought to be but don’t do enough to fix it. The last group, of course, includes the fans who gamble on races and support the sport financially.

During the years when drugs were allowed in racing, trainers could take advantage of the fact that the human medications they were using to prepare their horses for racing (painkillers, anti-inflammatories and other drugs) often bled over into the race prep and weakened the horse’s resistance to injury or pain. In addition, racing officials lacked the ability to quickly test for these substances and penalties were generally weak.

After the incident in which 30 horses died at Santa Anita, reforms were made and the sport moved to a different track but training and racing continue. Each year, tens of thousands of horses are killed in the United States, according to PETA, and many more die in Canada and Mexico. These deaths are a rallying cry for animal rights activists who call for the ban of the sport everywhere.