Dornoch, a heavy underdog, won the Belmont Stakes with 17-to-1 odds.Credit...Victor J. Blue for The New York Times

Summer at the Spa — a ritual nearly 200 years strong — started early in Saratoga Springs, N.Y., with the third leg of the Triple Crown, the Belmont Stakes, being held on Saturday for the first time at Saratoga Race Course, a revered relic where the elite and otherwise mingle, but the horses rule.

Broadway, the city’s central thoroughfare, bustled. Lines for picnic tables at the track formed before dawn. A new color — Belmont green — blended with the track’s signature red-and-white trimmings. Owners, trainers, horseplayers and the cooler-toting faithful all hailed the break from tradition for the race’s 156th running.

The 17-1 longshot Dornoch, ridden by Luis Saez and trained by Danny Gargan, held off Mindframe and Sierra Leone for a stunning victory.

The former Major League Baseball player Jayson Wirth and the other owners of Dornoch celebrated winning the Belmont Stakes.

Dornoch was hosed down after crossing the finish line.

Bettors placed their wagers before the running.