I've heard over 20 different Denver rappers and everyone of em' rep Midwest.
If they were to rename the United States regions today, I think a few states wouldn't be called Midwest no more.
If you really look at a map of the US, you'll see that the exact Middle is around Oklahoma City, OK or Witchita, KS. So anything left of OKC/Witchita would really be West and right of OKC/Witchita is where the East would start.
I don't think the heart of the M-Dubb is the Great Lakes region like somebody else said earlier. I think that's Kansas and Nebraska and shit. The Great Lakes region really leanin East like a mufucka. Lake Erie & Lake Ontario both touch New York.