American Pharoah has been named the United States Horse of the Year by a knockout, claiming all 261 votes.

The Triple Crown and Breeders' Cup Classic winner was also named the top three-year-old in another unanimous decision.

American Pharoah and his connections picked up five Eclipse trophies on US racing's biggest award night, with Zayat Stables prevailing in the owner and breeder divisions and Bob Baffert taking the award as top trainer.

The colt was the first to sweep the Kentucky Derby, Preakness Stakes and Belmont Stakes since 1978, earning nearly $US8.3 million ($A12.12 million) last year alone.

"We had a phenomenal year," Baffert said.

American Pharoah's year wasn't flawless. He was beaten in the Travers Stakes at Saratoga in August by Keen Ice, one of only two losses he would endure from his 11-race career before being retired to Coolmore's Ashford Stud in Kentucky.

Votes were taken from the National Thoroughbred Racing Association, Daily Racing Form and the National Turf Writers And Broadcasters.

"I keep saying it," Baffert said. "There was something special about American Pharoah."

The only division where Pharoah's team was beaten on Saturday (Sunday AEDT) was in the jockey race, where Victor Espinoza finished second behind Javier Castellano.

Baffert's Eclipse Award was his fourth and he became the fourth trainer to win at least four times, joining joining seven-time winner Todd Pletcher, five-time recipient Bobby Frankel and four-timers Laz Barrera and D Wayne Lukas.

Baffert said he didn't think he would ever win another Eclipse, and actually dropped the trophy before congratulating the other finalists, Pletcher and Chad Brown.

"You guys were looking really strong, had a great year," Baffert said. "Until June 6."

That was the day American Pharoah won the Belmont, and punched his ticket to racing immortality.

And to think there was some concern when 2015 started as to whether American Pharoah could run at all, a deep bruise that kept him from the 2014 Breeders' Cup threatening his potential availability for the Triple Crown.

Last year's juvenile Eclipse winner dodged another bullet in a lead-up to the Derby, racing with a bent shoe and somehow not only winning but escaping without injury.

"Everything about his story, and about his year, was fantastic," Baffert said.