High Quality Content by WIKIPEDIA articles! Santa Anita Oaks is an American Grade I Thoroughbred horse race held annually in late March at Santa Anita Park in Arcadia, California. Open to three-year-old fillies willing to race 8.5 furlongs (1 1/16 miles) on the dirt. The race is a Grade I event with a purse of $300,000 and has been a prep race to the Triple Tiara of Thoroughbred Racing, including the Kentucky Oaks, the Black-Eyed Susan Stakes and Mother Goose Stakes.