Undefeated Justify won the 144th Kentucky Derby on Saturday, ignoring the wettest conditions in race history to become the first Derby champion since 1882 who didn't race as a two-year-old.
Trainer Bob Baffert won the Derby for the fifth time, one shy of the record owned by 1940s legendary trainer Ben Jones, while jockey Mike Smith captured his second victory in the 1 1/4-mile classic at Louisville's Churchill Downs.
"It took a great horse to do what he did today," Baffert said. "I rank him up there with my top ones. We knew we had something special."
Favored Justify, who went off at 5-2 odds, unleashed the third-fastest half-mile pace in Derby history and went on to win in 2mins 4.20 secs with Good Magic second by 2 1/2 lengths, edging third-place Audible at the line.
Mendelssohn, trained by Ireland's Aidan O'Brien and hoping to become the first Europe-based horse to win the Derby, was last in the 20-horse field before 157,813 spectators.
Justify, who improved to 4-0, became the first horse since Apollo some 136 years ago to win the showdown for three-year-olds without running the year before.
"It would take a horse like him to break that curse," said Smith, whose other Derby win came in 2005 aboard 50-1 longshot Giacomo.
"Wow, I don't have the words to describe what makes this horse so special. He is just so big and talented. He has got the mind for it."
Justify captured the opening leg of US flat racing's Triple Crown, which continues in two weeks at the Preakness in Baltimore, Maryland, and concludes with next month's Belmont Stakes in New York.
Only 12 horses in history have swept the treble, Baffert-trained American Pharoah being the most recent in 2015.
"I think this horse is as special as American Pharoah to win a race like this, especially the way he did it," Baffert said.
Despite a muddy track that absorbed a Derby-day record three inches of rain and intense downpours as horses were loaded into the starting gates, Justify broke well, starting seventh from the rail and settling into second behind early leader Promises Fulfilled.
Justify took the lead on the far turn and charged into the backstretch. Good Magic chased in pursuit but never had a move to prevent him from becoming the sixth consecutive favorite to win the Derby.
Baffert admitted the wet conditions had him concerned.
"This track had me worried but we saw something special," Baffert said. "When he got away I knew we had a chance."
Justify's dazzling outings this year included a superb three-length victory at last month's Santa Anita Derby.
While O'Brien found misery in Kentucky, there was some comfort. O'Brien-trained Saxon Warrior won the 2,000 Guineas in England on Saturday.