“It came right down to just the spirit of men and dogs against nature,” Gay Salisbury said.

A noted racer and mining-company dog driver named Leonhard Seppala was originally assigned half of the Nenana-Nome distance. Seppala’s lead dog, a gray and brown Siberian husky named Togo, had covered 4,000 miles in one year alone, guided a famed polar explorer around Alaska, and won major races. Togo had been Seppala’s lead dog since he was 8 months old; now, at age 12, Togo would have one of his final Alaska outings with his driver.

Seppala, Togo and the team set out at high speeds, running a total of 261 miles — they carried the serum for almost double the length any other team did. Twice, to save time, they violated warnings to avoid Norton Sound, a dangerous inlet of the Bering Sea, and instead went straight over the frozen sea, where ice often separated from shore, stranding travelers on floes. In the dark, in 85-below temperatures with wind chill, Seppala could not see or hear the cracking ice, and was dependent on Togo, the Salisburys wrote.

Meanwhile, worried that Seppala’s dogs would get too tired, Alaska’s governor called in additional drivers for the final portion. Just five and a half days after the serum left Nenana, a driver named Gunnar Kaasen and a lead dog named Balto pulled into Nome, serum in hand.

“It was Balto who led the way,” Kaasen told a reporter. “The credit is his.”

Kaasen and Balto, a handsome black Siberian with white paws, became instant heroes. There were front-page articles; commendations from the president; tributes from the Senate; newspapers (including The Times) printing a report that Balto had died from frozen lungs, then quickly rescinding it; wishful editorials proposing that Balto appear at Westminster; a national tour; a Hollywood contract.

But as Kaasen, Balto and that team of dogs were becoming celebrities, the other mushers from the relay straggled into Nome with a different story. Kaasen was assigned the next-to-last leg. But, in an account that some mushers still doubt, Kaasen said the lights were off in the cabin where he was to hand off the serum, so he headed for Nome himself.

Seppala was already broken when he arrived — he had lost Togo when the dog ran off after a reindeer. Then he found that not only were Kaasen and Balto on their way to Hollywood, but the newspapers had attributed Togo’s lifetime feats to Balto, a dog he had not considered decent enough to put on his 20-dog team.