My father's side of the family first settled in Detroit (they were sponsored by my grandmothers sister who had emigrated to the US when my grandmother was an infant). My grandparents stayed in the Detroit area until we moved my grandmother to be closer to my parents when she couldn't live on her own anymore (she lived to 101).
My dad and his brothers all left Detroit for graduate school. They found it to be rather provincial and my dad remembers having trouble with girls not wanting to date him because he didn't "want to be an engineer for the automotive industry" (he is a retired academic, as were both of his brothers). Note; my father was a young adult when he came to the states in the 50's.
My point is, it really was a one industry town, at least in mind, if not actuality. Of course, Detroit proper suffered as factory technology switched to single-floor layouts and needed more space and preferred building on greenfield sites rather than rebuilding existing factories (obviously you couldn't close down a plant to rebuild it with much ease). And of course the ugly R word has a lot to do with that problems, much like Gary over in Indiana.
