The novel takes place primarily in the Yukon—Northwestern Canada and Alaska. The social and political backdrop is the Klondike Gold Rush. In 1896, seven years before the novel was published, miners discovered gold in the Klondike area. Roughly 100,000 people flocked to the area, largely from cities up and down the West Coast of the United States. There was little infrastructure for the sudden influx of people, which led to "boom towns," or sudden temporary settlements that popped up (Dawson City, for instance, is one of these). Traveling between towns was arduous and generally required a team of sled dogs. Buck is kidnapped from a comfortable estate in California and brought to the Yukon to work as a sled dog.
London uses the setting to comment on harsh laboring conditions, and the way greed inspires employers to abuse their workers and treat them as fungible. The prospectors in the Yukon will stop at nothing on their way to riches, even though the gold rush resulted in far more stories of ruin than riches. Buck is passed from one master to the next and is seen more as a commodity and a means to gold than as a living being with an inner life. Most of his masters compromise any sense of morals in their treatment of him and the other dogs, and they still fail to find much gold. Buck learns to work hard and look out for himself because no one else is going to do so for him (except for Thornton). The gold rush is the perfect backdrop for London to show how the aggressive pursuit of wealth, on an individual or a corporate basis, often results in more cruelty and tragedy than payoff.
London's sense that people should be treated with dignity and respect does not extend to everyone. Although he mainly focuses on the relationship between dogs and humans in this novel, he also incorporates First Nations people into the setting. He represents them as a violent part of the natural environment rather than as people whose home has been invaded by the prospectors and the dogs they bring. Eventually, some First Nations people kill Thornton, the man with whom Buck had the most reciprocal relationship. London treats this event as Buck's final nudge from his cruel environment into life as a wild animal. London's racist characterization of the First Nations people as environmental obstacles demonstrates the limitations of his otherwise progressive labor politics. These limitations are even more obvious in some of London's other works.