Horse racing is one of the oldest sports, and it has undergone little change over the centuries. It’s also one of the most fascinating, because it has developed from a primitive contest of speed or stamina into an enormous entertainment business with worldwide appeal.

But horse races are not always conducted the way you might expect. For example, there are a number of ways to bet on a race, including placing bets to win, place, or show, which involve placing multiple bets at any time during the race. For some fans, betting is the main reason for attending a race.

In the days leading up to the race, Siena’s central square is transformed beyond recognition. A gritty mixture of clay and earth is packed over the golden cobbles, creating a compact and level track for the horses and protecting the ancient tiles beneath. Bleachers are assembled for thousands of spectators, and barriers are erected to mark the course.

Racing historians have some helpful context for the event. Selima was a spirited mare, trained by the legendary George Gilcoyne in Maryland, and owned by Colonel Richard Nicolls, the leader of the British occupation force that established organized racing in the colony of Virginia. The decision to enter her in the race was a rousing political act: Maryland breeders believed their racing was superior to that of Virginia, and they had no patience for the southerners’ arrogant attitude.

During this era, the sport was heavily influenced by the British. Winners of races were awarded a silver cup and handicapping—a system in which the winning horse carried more weight than the runners-up—was common. Large mature horses were preferred and, until the Civil War, stamina was regarded as more important than speed.

Horse racing’s popularity waxed and waned with prosperity and depression, war and peace. It experienced a major resurgence in the 1960s and 1970s as great horses like Secretariat, Seattle Slew, and Affirmed thrilled crowds at the tracks.

The recent spate of equine deaths, most notably 30 at Santa Anita in California last year, has renewed public concern about the safety of the sport. In response, many states have begun to require necropsies after every race to better understand what goes wrong. Some have even started to collect data on equine injuries and fatalities, and California and New York now have public databases that catalogue equine accidents and deaths.