Minneapolis, Kansas City, Indianapolis, Omaha, Des Moines, and Sioux Falls are the most Midwest feeling cities.
Chicago, Milwaukee, Green Bay, Duluth, Detroit, and Cleveland are all Great Lakes cities which make them feel different than the Midwest in a variety of ways. St. Louis, Louisville, and Cincinnati are all a combination of Midwest and Southern.
You go much farther north from Minneapolis and it doesn't feel like the Midwest anymore. You start to go west from Sioux Falls, Omaha, or Kansas City and it doesn't take that long to feel like you are out of the Midwest. And if you go south or east from Indianapolis you get outside the Midwest.
View attachment 171225This would be my rough map for places that feel distinctly Midwestern. An actual map wouldn't have quite as smooth of lines and would have a few places cut out. If nothing else Iowa is definitely the only wholly Midwestern state. Now if you wanted to argue about if the southern half of Minnesota is the most Midwestern place or if Kansas City is the most Midwestern big city or if large parts of Illinois or Indiana are the most Midwestern places, those are arguments that can be reasonably had.