This image is a colorized photo of the end of the Chicago Drainage Canal 28 miles from Chicago.
The description states:
Butterfly Dam at Lockport, the end of the Chicago Drainage Canal is 28 miles from Chicago. The length of the completed main channel is 28 miles. The right of way approximates 6,500 acres and cast nearly $2,500,000.00. The entire cost of the canal was over $30,000,000. By use of the drainage canal the current of the Chicago River is reversed and the pure water of Lake Michigan dilutes with its enormous volume and active flow the sewage of the city of Chicago, and bears it away in harmless form.
–In other words, this is a sewage drain that uses Lake Michigan water to dilute the concentration of the sewage and discharge it into the Des Plaines River. While this is far from a desirable treatment method, it is still in use and continues to direct sewage down the Mississippi watershed.
This card was used and is dated 1926.