Chicago River Mouth

For most of its history, the Chicago River sluggishly moved water from the plains to Lake Michigan. When raw sewage and other pollutants were dumped in the river, they flowed into Chicago's primary source of drinking water. As the city grew, fear of disease spread, and officials decided to permanently reverse the river's flow, sending its polluted water to the Mississippi River instead.

A 28-mile-long canal was built between the Chicago River and the rivers that drain into the Mississippi. The canal was designed to get deeper as it moves west, allowing water to flow from the Chicago River. When a steam shovel removed the last of the dirt separating the river from the Chicago Sanitary and Ship Canal on a cold January morning in 1900, the river emptied into the canal and began pulling water from the lake.

The eight-year project was named one of the seven wonders of engineering by the American Society of Civil Engineers in 1955. In 1999, the society called the Chicago River system a "Civil Engineering Monument of the Millennium."

Watch a six-minute documentary on the reversal of the Chicago River.