I'm not sure if the lack upward mobility in the South is a result of our economic landscape. It plausible that it's due to the lingering effects of segregation and the fact that the vast majority of our bottom 20% are African Americans while the majority of the top 20% are Caucasian. This map and a map of the distribution of the African American population in the South correspond so well it's a little disheartening.
I think you'd see the same distribution in the North, though. Reminds me of a joke about the difference between white Southerners and white Northerners... the southerners don't care if blacks are around, so long as they aren't uppity. Northerners don't care if they're uppity, as long as they're not around.
http://www.slate.com/content/dam/slate/blogs/moneybox/2013/0...
http://prisca.me/wp-content/uploads/2012/11/Percent_Black-20...
http://prisca.me/political-plankton-the-left-behind/