Robert Browning words,
Ah, but a man's reach should exceed his grasp, or what's a heaven for?
certainly characterize the dream of Lennie and George. In order for their desperate lives to have some hope, George recites the words of the dream for Lennie; in order for him to derive the satisfaction of child-like imagination, Lennie has George recite this dream. It is this dream and their friendship which gives meaning to the lives of the two men, significance that is missing for the others.
Thus, the significance of the dream is that it gives Lennie and George a reason to work and to live. In the setting of the Great Depression, in which Steinbeck's novella is set, the plight of the displaced white male was great; in fact, thousands were alienated and alone. Living lives of "quiet desperation" as Thoreau wrote, these men who once pursued an unattainable American dream now sought refuge in fraternity with one another. Woody Guthrie, who traveled thousands of miles by railway, sang of this loneliness and despair while bringing men together. In order to escape these feelings of alienation, men like George entertained a dream that, although they did not believe in it, provided them some hope. But, once Lennie dies, so does the dream as George can no longer even sustain any hope.
The dream of the farm in the novelette Of Mice and Men is used to show that George and Lennie are different than all the others around them. They have hope and a real plan. Lennie just likes soft things so he longs for rabbits on the ranch, but George is aware that it will take more than rabbits to feed him and Lennie.
The ranch may have never actually happened but once Candy was going to contribute, the plan seemed to be coming to life. The dream is that one special thing that all men want but just can't seem to reach. It was so close that George could almost touch it, and then it was gone.