Victor Espinoza will donate his Belmont Stakes winnings to City of Hope in Duarte, California, a cancer research and treatment centre.

He'll keep something much more valuable: a place in history.

As the jockey of American Pharoah, the first Triple Crown winner since Affirmed in 1978, Espinoza called it "the best feeling I ever had," when the colt was only through the first turn.

A tad slow out of the gate in the Belmont Stakes, the Kentucky Derby and Preakness winner seemed to glide to the lead in just two strides.

In his third Triple Crown try on Saturday (Sunday AEST), Espinoza was on the best horse and never had reason to doubt it.

"It's just an amazing feeling that you have when it's 20 yards out of the wire and you're three or four lengths in front," Espinoza said.

He rode War Emblem, also trained by Bob Baffert, to eighth in 2002 and California Chrome a year ago for fourth as both colts tried to win the final Triple Crown leg.

"Two times, I feel like a loser," Espinoza said.

But this time around, everything felt right even before the race.

"Warming up he was just class," Espinoza said.

"He walked into the gate, amazing. "He was ready today."

Espinoza grew up as one of 12 children on a farm outside Mexico City where he once worked as a bus driver.

He first started winning at Mexico City's Hippodromo de las Americas and moved to Northern California in the early 1990s and then to Los Angeles where his career really got going in 2000.

Espinoza appeared on the National Museum of Racing and Hall of Fame's ballot for the first time this year but didn't get in.

Now he owns the title of Triple Crown winner with many more honours sure to come.