I'm surprised Pennsylvania wasn't German. They're one of the few places where it was naturally cultivated, much like French was in Louisiana. Of course, Philly might drown that out.
I'm also surprised how much German is spread across the Plains... but in many places that may just be because English is SO dominant, and Spanish the next (and distant) runner up, that it's almost impossible to get any significant measurement for third.
Polish in Illinois surprises me, if only because most Polish Americans so rapidly segued into English that it's mostly a novelty. I'd've thought having Chicago would've produced something else.