The Original Chicago River

The North and South Branches once flowed into the Main Stem, which emptied into Lake Michigan.

The North Branch originated with three indistinct forks. These forks, called sloughs, were marshy, wet areas with little current.

The South Branch began at Mud Lake, the key to the area’s development. Here, Native Americans traveled between the Des Plaines River (which links to the Mississippi) and the Chicago River (which links to Lake Michigan). Except for the short periods when Mud Lake flooded its banks and connected the two rivers, people portaged it, carrying their canoes and goods over land.

As early as the 1600s, visitors contemplated the value of a canal to replace the portage. Had the Des Plaines and Chicago rivers not been so close and had a mountain—instead of a small hill—separated them, perhaps there might not have been a Chicago.