Atlanta would be another interesting one, as would New Orleans.
What are the arguments for these cities not being Southern?
Between the Catholicism and the heavy French/creole/Caribbean influence, New Orleans isn't culturally southern.
Well, is Cajun country not southern either?
Meh, as a whole no, but there are southern overtones.
That's really interesting, because generally if you think or speak about the American South in my part of the world, New Orleans with all that entails - Mardi Gras, New Orleans Jazz, Creole cooking, whatever - is like the first thing that comes to mind.