I don't know much about Southern cities, but I have lived in the rural South for nine years (Tuscaloosa, Alabama and Columbus, MS), and I believe that it is the rural South where Southern culture has originated, so that is what I'll talk about here.
I left Mississippi to go to college here in Pittsburgh. When I did so, my friend drove me to the airport and said, "So you're movin' up North, huh?"
"I've been up there before, and I'm gonna tell you that everybody up there is crazy -- you'll fit right in"
He was so right. Up here, culture is something completely different. It's something that people decide to belong to. There are so many different subcultures to chose from. In Pittsburgh, you can be a raver or a goth or a punk or a yinzer. There is no unifying Northern culture, people just do whatever they want.
In the South, you have just two cultures: Southern and not-quite-so-Southern. This basically amounts to rednecks (Southern) and everyone else. Everyone, however, shares the same sort of mindset discribed by hodgepodge, i.e., be hospitable because its the right thing to do. Be nice because you're s'posed to. Southern culture is this uniform mindset. Southern culture is tradition. Northern culture is diversity.