Potentially between Great Lakes cities (Milwaukee-Chicago-Detroit, though probably not Detroit as its a long detour through the Straight of Mackinac) or as fast riverboats.

Yeah, that dumb Milwaukee to Chicago flight. The Hiawatha doesn’t go to Ohare (an existing right of way, would add time a little bit of time to the main downtown to downtown trip, but it’s so dumb it doesn’t have at least a glenview to ohare connection), just the Milwaukee airport, and anyway I suppose airlines would rather you be in their system as soon as possible. But such a dumb flight. Take off, then land, hope you don’t spend more time taxiing than in the air.

I've needed to go to Kalamazoo several times, connecting through O'hare. On the return trip, because of the timezone change and the extremely short flight (~15m IIRC), the arrival time printed on your ticket is earlier than your departure time.

Buffalo NY (via Lewiston NY) <=> Toronto had a fast hovercraft service for some years. This might work there with a speedy transfer between Lewiston and Buffalo. Toronto to Rochester NY too. Erie PA.