Where is the lowest bridge that must be cleared with no alternate route around it?
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. 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.
