Lots of people seem to think that the Midwest is the land of accentless English. This is simply not true. If you speak a language, you speak a variety of that language. It doesn’t matter where you live.
In fact, many parts of this country that are traditionally considered to be midwest are undergoing radical changes in their vowel systems. Research by big-name sociolinguists (Dennis Preston, William Labov, and others) on the Northern Cities Shift (NCS) in Michigan has shown complete reversal of the vowel sounds in bed and bad, for example. Meanwhile, several of us who studied under Dr. Preston have shown that this shift, which was thought to only affect White speakers, can be documented among Mexican Americans (e.g. research by Becky Roeder and I), among African Americans (e.g. research by Jamilla Jones), and by Lebanese Americans (e.g. research by Jon Bakos) and Polish Americans.
Here’s a link to research in neighboring Ohio, where PhD candidate David Durian is looking at a different set of changes in the vowel systems in Columbus. Among others, he suggests that the vowel in boat is being produced with the tongue further front in the mouth than we might otherwise expect, particularly among the younger women in his study.