Seavey turned 25 on March 4, the day the race officially started north of Anchorage. He was the first musher to reach Nome, his nine dogs trotting under the famous burled-arch finish line in the Bering Sea coastal community at 7:29 p.m. Tuesday.
The winner greeted family and friends briefly, then turned to hug his dogs.
"They mean the world to me," said Seavey, of Willow, about 50 miles north of Anchorage.
"I could not be prouder of these guys. It's hard to not come to tears when they finally crossed under this arch in first place."
He finished in nine days, four hours and 29 minutes.
"When you put your mind on something ... good things will happen," he told the crowd.
"Dream big!" he said as he sat with an arm around each of his two lead dogs, Guinness and Diesel, who wore their own yellow floral garlands. "Go for it! Why not?"
The previous youngest winner was the race's only five-time champion, Rick Swenson, who won his first Iditarod at age 26 in 1977. Swenson, now 61, is in this year's race, and was running in the middle of the pack.
Asked about his record-breaking victory, Seavey said it's been a goal since he started racing competitively.
He said his race strategy was to build position carefully.
Heading into the Ruby checkpoint, Seavey thought his team "had a real possibility of winning." Still, while he felt confident, "it's not over till you're sitting on the podium," he said.
Of the race's latter stages, when mushers are notoriously sleep-deprived, Seavey said, "every light that I thought I saw, I thought it was the headlights of a musher about to pass me."
"When you have Ramey Smyth and Aliy Zirkle behind you, it doesn't matter if they're a half day behind you. You'd better be looking over your shoulder," he added.
Zirkle finished second, Smyth was third.
It's a family affair for the Seaveys. Dallas' father, Mitch, 52, won the race in 2004. He was racing in seventh place when Dallas crossed the finish line.
This year, Dallas' 74-year-old grandfather, Dan, is running in his fifth Iditarod to celebrate the 100th anniversary of the Iditarod Trail. His trip to Nome is being sponsored by the Iditarod Historic Trail Alliance to highlight the rich history of the trail.
"It's kind of what we do," Dallas Seavey said when asked about that legacy.
Long hours, months and years of training with the dogs brought musher and team to this point.
"I feel like, somewhat like these dogs, I've been raised for this as well," he said.
Two of 1978 winner Dick Mackey's sons have also won, Rick Mackey in 1983 and Lance Mackey from 2007-2010.
Dallas Seavey was the first musher to leave White Mountain after completing a mandatory eight-hour layover to rest his dogs. The second musher out was Aliy Zirkle, and Dallas Seavey maintained his lead for the last 77 miles of the trail from White Mountain to the finish line in Nome.
Dallas Seavey has been described by his father as "fiercely competitive." The former Alaska high school wrestling champion, who also spent a year at the U.S. Olympic Training Center before turning his attention back to dogs, was the first musher to reach the White Mountain checkpoint at 12:14 a.m. Alaska time.
Sixty-six teams began the race on March 4. Eleven mushers have scratched, including the latest, Tom Thurston of Oak Creek, Colo. He left the race Tuesday afternoon in Unalakleet over concern for his dogs. He was down to eight dogs when he scratched.
Among the 55 mushers still racing Tuesday were 12 rookies. Brent Sass was doing the best among the rookies, in 13th place.
The 32-year-old is originally from Excelsior, Minn., but moved to Fairbanks, where he operates Wild and Free Mushing, his kennel and guiding business.