Smarty Jones' quest to become the first American Triple Crown winner for 26 years ended in disappointment at Belmont Park when the colt was worn down and beaten a length by 35-1 outsider Birdstone.
The John Servis-trained colt, an imperious winner of both the Kentucky Derby and the Preakness Stakes, was sent off a 1-5 chance to stretch his unbeaten record to nine in the mile-and-a-half contest.
And turning for home the dream looked like coming true as he still held a four-length advantage under Stewart Elliott.
However, the Nick Zito-trained Birdstone had made a huge move round the top bend under Edgar Prado and gradually he reeled in Smarty Jones to spoil the party.
Throughout the day, a crowd of more than 100,000 had assembled at the New York track and by the time of the Belmont, which was delayed by the misbehaviour of Rock Hard Pen at the gate, the excitement had reached fever pitch.
Afterwards, Smarty Jones' connections took the defeat on the chin. Elliott said: "I was trying to get him over a little bit early on, but I had horses running on the inside of me. I was trying to get the horse to relax and slow down.
"I was still sitting with some horse down the back and trying to be patient and wait. They were pushing me, but I still felt comfortable. At the top of the stretch I had some horse under me and he responded and never stopped running. I saw Birdstone running, but we just couldn't hold him off."
Servis said: "It was not to be for my horse and it hurts, but we had a really good run and we can put our hands down and be proud of him.
"We did a good job but there was a lot of pressure on him early. I was a little concerned as he didn't look to settle as well as he had in his previous races and I wasn't happy down the back side.
"The one thing I was worried about after the Preakness was that he was too sharp."
Plans for Smarty Jones are in abeyance, although his connections would love to run him in their own Pennsylvania Derby.
Meanwhile, Zito said of the winner: "I feel great. We got it right for the right people and as for John Servis, he is a class guy and he did a great job. Smarty Jones will always be one of the most famous horses."
Smarty Jones was attempting to become the 12th winner of the Triple Crown and the first since Affirmed in 1978. The loss cost connections huge bonuses including the $5 million Visa Triple Crown pot.