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.)
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
