Country House was declared the winner of the 145th Kentucky Derby at Churchill Downs on Saturday when Maximum Security became the first horse in the history of the race to be disqualified after crossing the line first.
Country House's team raised an objection to Maximum Security's win, saying the 9-2 favorite's wide turn heading into the stretch impeded other horses on the sloppy track in rainy Louisville.
After a review, officials found Maximum Security was guilty of a contact foul and awarded the win to the William Mott-trained Country House.
Code of Honor was bumped up to second and Tacitus third.
"No words can describe this. It's amazing," Country House jockey Favien Prat said after learning he had won his first Kentucky Derby.
"I really lost my momentum around the turn," he said of Maximum Security's foul, which came when the colt veered from the rail just as several horses were gaining ground on the leader.
The result spelled heartbreak for Maximum Security trainer Jason Servis and jockey Luis Saez, who thought they had won their first Derby before a 20-minute video review changed the outcome.
Servis and Maximum Security owner Gary West told Sports Illustrated they planned to purse any available appeals to protest the disqualification.
The field was one of the most wide open in years after favorite Omaha Beach was scratched on Friday due to a breathing problem but few expected 65-1 Country House to take the prize and become the second-biggest outsider to ever win the race.
Donerail, at 91-1 in 1913, was the biggest longshot to win the Derby.
Coming into Saturday's race, Country House had only notched one win in six starts.
"It feels pretty darn good," veteran trainer Mott said of his first career Derby win.
"It was an odd way to do it and we hate to back into any of these things. It's a bittersweet victory but I've got to say our horse ran very well and our jockey rode very well."
Hall of Fame trainer Bob Baffert, who had a trio of horses in the race, had looked to secure a record-tying sixth Derby victory but it was not to be as Improbable came in fourth, Game Winner fifth and Roadster 15th.
The 1-1/4 mile race, called the "fastest two minutes in sports," featured the largest guaranteed purse of $3 million and played out before more than 150,000 fans that packed the grandstands and infield of Churchill Downs despite the wet weather.
Saturday's race came at a time when the sport has come under scrutiny following the death of 23 horses at the famed Santa Anita track in Southern California since Christmas.
The spate of fatalities has prompted an investigation by the Los Angeles County District Attorney's Office and led to protests by animal rights activists at the track, which is scheduled to host the Breeders' Cup in November.