A small working ranch in the Salinas Valley of northern California, sometime during the 1930s.
(Click the setting infographic to download.)
This is no sprawling, Dickensian novel with multiple plots and characters moving all over London. The setting is almost as small and confined as the plot; it occurs over a period of three days in four specific locations: a wooded area next to the Salinas River, a bunkhouse on the ranch, the stable hand's room on the ranch, and the main barn on the ranch. In fact, it's so tightly constructed that it could easily be a play. (Check out "Symbols: Morality Play" for more on the way Of Mice and Men might be like a play.)
But there is a larger background to the novel's setting: the Great Depression, which left people all over the country (especially men) poor and desperate for work. This poverty makes the characters suspicious and distrustful: there literally isn't enough to go around. Against this backdrop of suspicion and isolation, Lennie and George's friendship seems even more remarkable—and even more doomed.