Actually there are probably more dead mobsters outside of Detroit. The old timers around here have stories.
It's called the Union Corse ~ and they are still there, even in Western Tennessee, Cincy, Pittsburgh ~ Detroit, Toronto, and so forth. Many of the old old families have married into the newer families so it's hard to tell who is who.
Detroit's suburbs are certainly a burial ground for mobsters all the way back to the beginnings of the fur trade.