The following human beings appear in the book:
Judge Miller Buck's owner; a man who owns a huge plantation in California's Santa Clara Valley.
Molly and Alice Miller The Judge's daughters, whom Buck protects when they go on long walks.
Manuel A Mexican; one of the Judge's gardener's helpers. Because of his mounting gambling debts, Manuel steals Buck and sells him to a ring of dognappers.
The Man in the Red Sweater An unnamed person whom Buck remembers for the rest of his life because this is the person who teaches Buck the lesson that "a man with a club was a lawgiver, a master to be obeyed."
Perrault and François Two Frenchmen who are Buck's first new masters. They work for the Canadian government, delivering dispatches to outposts throughout the frozen North.
A Scotch Half-Breed Buck's second master; he delivers mail in the North. He is a competent master, but because of the demands made on him, he has to overwork the dogs.
"Black" Burton A vicious man who attacks Thornton; he, in turn, is attacked by Buck.
An Ape-like Man A "hairy" man with a bent back; he accompanies the Scotch half-breed on the mail routes.
Charles An inept middle-aged master of Buck's; Charles comes from the South, and he does not understand the ways of the North or how to handle dogs.
Mercedes Charles's wife; she attempts to live in the North as if she were on an "extended social camping trip."
Hal Mercedes's brother; he carries a whip, a gun, and a knife, and he is cruel to Buck.
John Thornton The man who rescues Buck from Charles, Hal, and Mercedes; he is the man to whom Buck becomes immensely devoted.
Hans and Pete John Thornton's partners; they accompany him on his expedition for the lost gold mine.
Matthewson The man who bets Thornton that Buck cannot pull a thousand-pound loaded sled.
Jim O'Brien John Thornton's friend; he lends Thornton a thousand dollars to make the wager with Matthewson.
The Yeehats A fierce tribe of Indians who murder John Thornton and his partners, Hans and Pete.
