Since the 19th century, many have tried. Some even have come close.
But only these 12 horses have won horse racing's Triple Crown: the Kentucky Derby, the Preakness and the Belmont Stakes in the same year.
2015: American Pharoah
Starting from the fifth post position, American Pharoah defeated Frosted by 5 1/2 lengths in the 147th Belmont Stakes, ending a 37-year Triple Crown drought.