Gavin Stevens includes "Cambridge" on his list of schools - "Heidelberg or Cambridge or Jefferson High or Yoknapatawpha Consolidated" (172) - in reference to Harvard University, in Cambridge, Massachusetts. Gavin went to college there before going to Heidelberg for graduate work.
In "Knight's Gambit" Gavin Stevens mentions Hollyknowe as an example of the kind of place in which young Mississippi women grow up. Hollyknowe is a small rural town west of Oxford.