The most valuable races run at the Breeders' Cup are currently the Breeders' Cup Classic, worth $6 million in prize money, and the Breeders' Cup Turf, worth $4 million. Both races are open to horses aged three years and upwards, but the Breeders' Cup Classic is run over a mile and a quarter on dirt, while the Breeders' Cup Turf is run over a mile and a half on turf, by way of making it more appealing to horses trained outside North America. Arguably the most famous horse in Breeders' Cup history was American Pharoah, trained by Bob Baffert. In his three-year-old campaign, in 2015, American Pharoah won the traditional North American Triple Crown – that is, the Kentucky |Derby, Preakness Stakes and Belmont Stakes – plus the Breeders' Cup Classic, to complete what has become known as the 'Grand Slam of Thoroughbred Racing'.