There is a real Mount Vernon in northern Mississippi. Measured from Oxford, the original of Jefferson, it is eighteen miles to the southeast. In Flags in the Dust it is referred to as a "hamlet" "six miles away" from the MacCallum place, where the "young woman" whom Lee MacCallum is courting lives (350-51). The MacCallums live over fourteen miles northeast of Jefferson, so by putting his 'Mount Vernon' even further away from his version of Oxford - i.e. from Jefferson - Faulkner may be trying to disguise the relationship between reality and his fictional re-presentation of it.
The place called "Haley bottom" appears only in As I Lay Dying, the third Yoknapatawpha novel. Although it is the first text in which Faulkner calls his county "Yoknapatawpha" (203), it is clear that he is still working out the topographical details of this new world. Once the Bundrens cross the flooded river, they should be able to travel straight from Frenchman's Bend to Jefferson. But according to Armstid, "the levee through Haley bottom had done gone for two miles and . . . the only way to get to Jefferson would be go around by Mottson" (185).
There are two "Whiteleaf" creeks in the fictions, or one that seems to flow in two different directions - and a hamlet named "Whiteleaf" as well. There's no obvious way to see how these three locations might be put in any one place on a map. In As I Lay Dying "Whiteleaf" refers to a creek that the Bundren's cross over between their farm and Samson's, where "the willows leaning near enough" to the road allow Cash to reach out of the wagon and break off a branch (109).
In As I Lay Dying the unseen character Miss Lawington lives somewhere in Jefferson, and it is probably at her house that she tells Cora that "the lady" who ordered the cakes for a party has changed her mind (7).
On their way to the cemetery in As I Lay Dying the Bundrens stop to borrow a shovel at a "little new house" from which Cash can hear music playing on a record player, or as he calls it, a "graphophone" (236). Anse goes into the house for the shovel, and also finds a woman there who the next day becomes "Mrs. Bundren," his new wife (261). We never learn her other names.
As the mule-drawn wagon carrying Addie's body in As I Lay Dying reaches Jefferson, the narrative provides a good sense of what it is like to enter the town from that side - at least in this one text. From the bottom of the "red sand" hill that rises to the plateau on which Jefferson stands, Darl can see "the massed telephone lines" and "the clock on the courthouse among the trees" that represent the town (229). Walking beside the wagon at this point, they see the first "negroes" who appear in the novel.
Located on a hill somewhere between Mottson and Jefferson, Gillespie's is where the Bundrens spend the last night of their journey to town in As I Lay Dying. During the night they move Addie's coffin from under an apple tree across the yard from the house to the barn. This barn is visible from the back porch of the house, where Dewey Dell and Vardaman sleep. In an attempt to end the journey, Darl burns it down.
Located on the outskirts of Mottstown near a branch, this "house" is where the Bundrens stop in As I Lay Dying to get water to mix the cement for Cash's leg (206). While this happens, the man who lives in the house watches from the porch. This is also where Jewel catches back up with the family on foot after returning his horse to Snopes in Frenchman's Bend.