See McDonough Marine's "Mileage Charts and Waterway Maps"
The lowest bridge that cannot be avoided on the Great Loop/Great Circle Route is 19.1 feet at mile 300.6 on the Chicago Sanitary and Ship Canal
after the Chicago River/Sanitary and Ship Canal and the Calumet Sag Channel join south-west of Chicago. This is the AT&S Railroad Bridge which is shown on the charts
as a swing bridge. It is inoperable and no longer opens. THERE IS NO WATER ROUTE
AROUND THIS FIXED BRIDGE FOR GREAT LOOP CRUISERS.
Pier 11 Marina, Chicago, at mile 323.2 Cal-Sag Channel, has a 60-ton travelift to 20' wide, 773-468-9605. They may un-step masts and lower radar
From Lake Michigan the Chicago River flows through downtown Chicago and becomes the Chicago Sanitary and Ship Canal. The lowest bridge through this route is 17 feet at mile 320.4, an inoperable bascule railroad bridge. The other route, the Cal
Sag Channel, has a bridge height restriction of 20-something feet.
Either way you must be able to clear the 19.1 feet fixed bridge mentioned above which is down river of both channels.
Tennessee River/Tenn-Tom Waterway has lots of bridges at 52 feet vertical clearance.