The nearly 1,000-mile (1,600-km) Iditarod Trail Sled Dog Race kicked off a day earlier when 69 mushers and their canine teams made a ceremonial jaunt through Anchorage.
The business end of the race began in Willow, a small community about 50 miles north of Anchorage, where the teams embarked in a journey across the Alaskan tundra that the fastest will compete in a little over nine days.
After Willow, the next checkpoint was 42 miles away at the tiny settlement of Yentna Station, with Danny Kaduce reaching it the quickest time and then setting off for the next checkpoint.
The race commemorates a 1925 rescue mission that carried diphtheria serum by sled-dog relay to the coastal community of Nome, which remains the final destination in this 42nd edition of the event.
Seavey, 54 and born in Minnesota, is racing for the 20th time. He said he was following in a path blazed by his father, Dan, who ran the inaugural race 42 years ago.
"I love the lifestyle," Seavey said. "Being able to raise four boys as mushers has made it very rewarding."
Competitors brave darkness, steep climbs and temperatures well below freezing. Distances between teams will grow along with the isolation.
The mushers, most from Alaska, will travel in stages of between 18 miles and 85 miles as they guide teams of dogs from Willow northwest through 21 other Alaska villages on the road to Nome.
There are mandated rest stops along the way.
Competitors include twin sisters Anna and Kristy Berington of Kasil of Alaska, with entrants coming from Norway, New Zealand, Australia, Canada, Sweden and Jamaica.
"From a race fan's standpoint, somebody who is really dialed into the competition, I expect it to be a thriller," said Stan Hooley, the race's executive director.
The winner usually crosses the finish line to a hero's welcome in slightly over nine days. Officials hold out until the last team crosses, which could be another week after the winner arrives in Nome.
This year, the winner will receive $50,400 and a new truck, while other top finishers will take home cash prizes from the race purse, which exceeds $650,000.
Six mushers in this year's competition have won an Iditarod and a quarter of the participants are rookies.
Norwegian musher Robert Sorlie, 56, is also one of the pre-race favorites, having competed in four Iditarods and won twice.
Sorlie returns to Alaska after being away from the race since 2007.
(Editing by Jon Herskovitz and Eric Walsh)