American Pharoah, with jockey Victor Espinoza aboard, won Saturday's 141st running of the Kentucky Derby at Churchill Downs in Louisville, Kentucky.
Firing Line ran second Dortmund placed third before a record crowd of 170,513.
The victory was Espinoza's second straight triumph at the Kentucky Derby win and his third Derby win overall.
American Pharoah was trained by Bob Baffert, as was Dortmund. This was Baffert's fourth Derby win.
The colt gave owner Ahmed Zayat his first Derby win after three second-place finishes.
"I'm speechless. We were very close before,'' Zayat said. "We are very blessed.''
The second jewel of U.S. horse racing's Triple Crown, the Preakness, is in two weeks in Baltimore, Maryland. The third race, the Belmont Stakes in Elmont, New York, is June 6.
No horse has won the Triple Crown since Affirmed won with Steve Cauthen aboard in 1978.