Okay, so I figured it must have something to do with large scale agriculture was introduced into the region, but not too long ago I wondered how come slavery hadn't been introduced into the US Mid-West for corn/maize farming and wheat farming. After all that would have made a certain amount of sense (thankfully it didn't happen though as that reprehensible institution might well have continued until the early 1900s-1950s).
So why exactly wasn't slavery introduced there?
Had it been introduced, how would that have changed the USA?