The gold rush in the Klondike region of Alaska and the Yukon territory of Canada began in 1896, and people flocked to the area with big dreams of getting rich. This region had barely been explored, and many of those who went there were ill-prepared for the conditions they had to face looking for gold. This is shown in the novel by Charles, Hal, and Mercedes. They are totally inexperienced in how to survive the ice and snow, and they pay for their ignorance with their lives and the lives of all of their dogs, except Buck. 

People will do strange things for money, and many went to the gold rush and risked their lives for gold and wealth. Many died, either from the elements, their ignorance, or as a victim of murder. Crime was high in the towns that popped up overnight. Those who couldn't find gold attempted to get rich by taking it from someone else. All of this implies the greed of people and the importance of attaining wealth in society.

This theme is as true today as it was then. Today we have the lottery, gambling, and criminals who want to get rich by taking from others. Wealth, and the lust for wealth, is a universal theme.