Ask people about language variation, and they generally start with the most stigmatized varieties in the South. They often don’t talk about variation within the South or within the North, but the truth is that there is a lot to talk about!
Here’s a link to a blog that documents language variation just within the state of Wisconsin:
The project is directed by Drs. Tom Purnell, Eric Raimy, and Joe Salmons (UW-Madison), and is helped out by a number of scholars, including Drs. Erica Benson, Joan Hall, and Kathryn Remlinger. The website explains ongoing research findings: everything from sounds (phonetics/phonology) to words to structure (grammar/syntax).
It also highlights Dr. Benson’s research on Wisconsonites’ perceptions of their own variation using perceptual dialectology methods developed by Dennis Preston.