You can take the girl out of Minnesota, but you can't take the Minnesota out of the girl... I spent 20 years living in Minneapolis/St. Paul, defending my voice from the inadvertent acquisition of a Minnesota accent. Granted, it's less pervasive in the cities - but the further you drive out of the cities in any direction, the stronger it gets. That includes you, Wisconsin. And especially you, North and South Dakotas. And Canada. Iowa, for some unknown reason, not so much.
And so to audition for and book a gig my first week back in L.A. that calls for a heavy MN accent was trickier than it seems at first glance. Here's hoping I did my home state proud.