Travelers from Lake Michigan can enter the Illinois Waterway at either Chicago Harbor via the Chicago Lock to the Chicago Sanitary & Ship Canal, or at Calumet Harbor via the Thomas J. O’Brien Lock to the Cal-Sag Channel.
Vertical clearance on the system is restricted to 17 feet on the Sanitary & Ship Canal and 19 feet on the Cal-Sag. The minimum overall horizontal clearance on the system is 80 feet. (Please refer to the Chicago Bridge Clearances in this section for more navigation information.)
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Illinois River Lock Mile Markers
Thomas J. O’brien Lock & Dam: 326.5
Chicago Harbor Lock: 327.2
Lockport Lock & Dam: 291.1
Brandon Road Lock & Dam: 286.0
Dresden Island Lock & Dam: 271.5
Marseilles Lock & Dam: 244.6
Starved Rock Lock & Dam: 231.0
Peoria Lock & Dam: 157.7
La Grange Lock & Dam: 80.2