I think that one would have to start with the idea that the ranch features men who come and go based on the presence of work. This reflects much in way of the condition of American workers in the Great Depression who sought work wherever and whenever it presented itself. There is little in way of roots and firm planting when there is such transition. At the same time, I think that one can see how the difficulty in saving money is present during the Great Depression. Obviously one reason for this is that there is little money being generated. Yet at the same time, life on the ranch depicts the men struggling to save a small amount, rather spending their meager earnings on distractions like drink and companionship with prostitutes. In the end, this becomes part of life in the Great Depression that Steinbeck brings out. I think that one major reason why the ranch can be seen as a smaller version of the Great Depression is the lack of solidarity that is evident on the farm. This is not because individuals dislike one another, although that can be said for Carlson and Curley. Yet, I think that this is because Steinbeck makes it clear that in times of economic distress, individuals demonstrate a greater tendency to reduce the bonds between one another in the need for economic survival. This is another reason why life on the ranch can be seen as a representation of the Great Depression. Steinbeck depicts this reality in a Socially Realist manner, depicting life as it is in the hopes of transforming it into something more along the lines of what can be.
The Great Depression began to end by 1939 because the war in Europe created industrial jobs in America. At first the U.S. was only selling military equipment and weaponry to Britain and France. Then it increased production for actual defense. More and more jobs opened up in ship building, munitions making, aircraft manufacture, and other war work. Also there were more and more men being absorbed into the Army, Navy, Marine Corps, Coast Guard, and Merchant Marine. Most of these men were white. The men who worked on the ranch in Of Mice and Men were almost all white, but they almost universally left agricultural work to get into higher paying war industrial jobs. They spoke English and some possessed needed skills. This created a huge labor shortage in California agriculture and elsewhere. The growers began recruiting workers from Mexico, and the Mexican population of California grew dramatically with legal and illegal immigrants as well as temporary workers who were supposed to return to Mexico after the harvest season ended. After World War II ended, the Mexican farm laborers had become firmly established in California agriculture, and the whites were not motivated to return to that kind of arduous, low-paying toil anyway. Industrial expansion after the war made opportunities in industry, building, auto assembly, and other fields available, especially for white males. The picture that Steinbeck painted in Of Mice and Men and in The Grapes of Wrath no longer was valid, although the Mexicans with their big families living in company-owned cabins and buying their food from the company stores was just as grim, if not more so. The Mexicans were barred from upward mobility by ignorance of English, by prejudice, often by illegal status, by lack of skills and lack of education. Their children, grandchildren, and great grandchildren are gradually overcoming these barriers--but this is a different story from the stories of John Steinbeck.