During the late 1930s, California was struggling not only with the economic problems of the Great Depression, but also with severe labor strife.
This novel, like a number of Steinbeck's novels, is topical and timely in its relation to certain social realities of his day. At the time this novel was written, America was continuing to endure the Great Depression.
While the nation was affected on many levels of society, the poor and labor class were especially hard hit. We see some of the effects of the concentration of capital (ownership of property and materials being focused into the hands of "the few") and the effects of a lack of material power.
The ranch hands dream of attaining some property of their own but meanwhile toil to produce goods that will benefit the ownership. The profits will not be shared with the ranch hands, as George bitterly complains.
The conflicts between labor and ownership were formalized by strikes for fair wages and were also explored in some of Steinbeck's other novels, such as The Grapes of Wrath.
Other aspects of the novel also reflect on the general social biases of the era, as seen in Crooks' isolation and ostracism (based on skin color) and Curley's wife's similar isolation (based on gender). Ideas of mental health and mental disability were also not very close to today's perspectives. Lennie's treatment articulates some of the views held in the 1930s.