Symbols are objects, characters, figures, and colors used to represent abstract ideas or concepts.

The Farm 

For Simeon and Peter, the farm is something to escape, a place where they toiled relentlessly and thanklessly and a place that has demanded their "blood an' bone an' sweat" throughout their lives. They don't have any pride in the farm or any desire to stay. For Eben, however, the farm represents his mother and his love for her. He sees the farm as his inheritance, though there doesn't seem to be any reason for his entitlement. Though he doesn't work the farm as much as his brothers and father, he views it as rightfully his, and he seeks to take possession of it in order to honor his mother.  

Cabot often talks of the farm and the work he's put into it. He doesn't express love for it as much as he does a hardened pride in how he's transformed it from "nothin' but fields o' stones." For him, the farm represents the hardness of God and life; it is something he endures, not something he enjoys. 

The West

The West, specifically California, is on the opposite side of the country, and at the time of the play in 1850, it was a land of opportunity due to the Gold Rush. Unlike life on their New England farm, life in the West symbolizes prosperity and easy living. Simeon and Peter speak of their desire to go to California, and the allure of gold in the West extends to the evening sky they notice in the first scene. It sets up the promise of the West and California as a sunnier, brighter, easier place, a sharp contrast to their grim, difficult lives on the farm.