I'm not sure I understand how you want to use this category, but my first reaction is that the category is not a particularly good idea.
The U.S. "Upper Midwest" is not a well-defined modern or historical region. (See the discussion of the definition at https://en.wikipedia.org/wiki/Upper_Midwest
.) If we created categories for "Upper Midwest" topics and include Minnesota, Wisconsin, Upper Peninsula Michigan, Iowa, and the Dakotas, I think we'd have to invite other members to create categories for other somewhat informally defined -- and overlapping -- regions. For example, I could imagine other members proposing the "Upper Great Plains" (Dakotas, Montana, and Wyoming) and the "Great Lakes Region" (New York, Ohio, Michigan, Ontario, Pennsylvania, Indiana, Illinois, Wisconsin, and Minnesota). The situation could become rather messy...
What's wrong with sticking with geographical categorization based on well-defined geographies, such as individual U.S. states or the historical Northwest Territory?