American Pharoah favored in race at Preakness Exercise rider Jorge Alvarez gallops Kentucky Derby winner and Preakness Stakes favorite American Pharoah at Pimlico Race Course in Baltimore, Thursday, May (AP Photo/Garry Jones)
LOUISVILLE, KY - MAY American Pharoah ridden by Victor Espinoza, comes out of turn 4 during the running of the Kentucky Derby at Churchill Downs on May 2015 in Louisville, Kentucky. (Photo by Andy Lyons/Getty Images)
War Emblem (February Dark brown stallion bred in Kentucky sired by Our Emblem was the winner of the Kentucky Derby and Preakness Stakes in Wavy Navy mare - daughter of War Admiral is the Great Great Great Grandmother.
BALTIMORE, MD - MAY Gary Stevens celebrates atop of Oxbow after crossing the finish line to win the running of the Preakness Stakes at Pimlico Race Course on May 2013 in Baltimore, Maryland. (Photo by Rob Carr/Getty Images)
California Chrome wins the second jewel in the Triple Crown. Only 34 other horses have won the Derby and Preakness combination. If he succeeds at the Belmont, he'll be only the to win that rare victory of all three races.