When it comes to horse racing in North America, no races carry more weight than stakes races, which include the most prestigious and richest events in the United States. A stakes race is open to thoroughbreds only and gets its name from the stake each owner must pay to enter a horse. The winner takes the largest share of the purse, which can top one million dollars in the largest and most prestigious races, with the host track often adding to the pool, making races like the Kentucky Derby among the richest single stakes events in the country. The single richest stakes event is the Belmont Stakes in New York, which has offered a combined purse of nearly eight million dollars across thirteen races on the card. Stakes purses are typically paid out to the top four finishers, and several stakes races can be run in a single day. Stakes events are regulated by the Thoroughbred Owners and Breeders Association, based in Lexington, Kentucky.