The U.S. Triple Crown in Thoroughbred racing has been swept by only 13 horses in the history of the sport. It takes a special racehorse to win the 1 1/4-mile Kentucky Derby, the 1 3/16-mile Preakness Stakes, and the 1 1/2-mile Belmont Stakes in a five-week stretch during the spring of a 3-year-old campaign. Let's take a look back at the 13 superstars in this slideshow below who were able to etch their names in the history books as Triple Crown winners.