The first part of "Barn Burning" takes place in an unknown county somewhere in the southern United States. The second part of the story is set in rural Yoknapatawpha County in the state of Mississippi. Yoknapatawpha is Faulkner's fictional creation and serves as the setting for a great number of his stories. How do we know the second part of the story is set in Yoknapatawpha? We know because de Spain is a recurring character in Faulkner's work, and from other stories involving de Spain we know that his farm is in that county.
Now, how do we know the story is set in 1895 or thereabouts? Well, the narrator says that thirty years ago Sarty's father hid in the woods for four years during the Civil War, which ended in 1865. So, 1865 + 30 = 1895. The story also projects at least twenty years in the future, in the following moment:
Later, twenty years later, he was to tell himself, "If I had told him they only wanted truth, justice, he would have hit me again." (29)
As we learn when Sarty's sitting on the hill at midnight, only four days have passed since his family arrived at the de Spain farm, plus one day of travel time. We have about a five-day story that goes back thirty years in the past and twenty years in the future.
Now to get deeper into the setting into the setting. "Barn Burning" seems concerned with contrasts, like the difference between Sarty's daytime life and his nighttime life. At night, unlawful activities are performed. Barn burning is our case in point. Sarty is always woken in the dark by Abner, either to act as his accomplice on some dark errand, or to get smacked around and lectured. After Sarty leaves it all behind, the dark becomes, at least for the moment, a place to sleep until he wakes naturally, and a place where birds sing in the arrival of morning.
The daytime scenes in "Barn Burning" seem to revolve around work and court. So long as Sarty is working, he's fine. It's when he's being forced to lie and otherwise act outside the law that he freaks out. Part of what makes Sarty run is the realization that no matter how hard he works, so long as he stays with his father, neither his days nor his nights are his own. Both are controlled by his father. Before he runs, night and day threaten to blend into a seamless nightmare that he must escape or lose himself completely.
Another interesting setting contrast is between the "unpainted two-room house" the Snopes family lives in and the de Spain mansion. The narrator tells us that the family has lived in twelve other homes just like the two-room house. But, the de Spain mansion is something different from homes of previous landlords. The contrast between that house and the one Sarty's family lives in so great it takes on almost divine proportion in Sarty's eyes.
The de Spain mansion is also a source of comfort to Sarty. He thinks that people who live in a fancy house like de Spain's are out of Abner's reach. What he doesn't understand is that Abner's poverty and de Spain's wealth are opposite extremes of the same system. Without men like Abner to work his farm for the skimpiest wages, de Spain wouldn't have a mansion in the first place. Far from being safe from Abner, the de Spains (or at least their barn) are the most likely target of the his wrath.