What’s a growing city to do when its water supply is jeopardized by its own filth? If it’s Chicago and it’s the late 19th Century, they reverse the flow of an entire river system. In the process they purposely punctured a Continental Divide.
I’m in Chicago this week so I wanted to make sure I got away from work for a few moments to explore a little local geo-history. Let’s look at the great Chicago Sanitary and Ship Canal. Most visitors stop by Grant Park, the Navy Pier, the Magnificent Mile and places like that. I, on the other hand, pay homage to the remnants of an open sewer.
The city still dumps treated wastewater into the Chicago River system. However, no doubt to the delight of visitors that take those tour boats through its skyscraper canyons, it’s a whole lot cleaner than what got sent through here a century ago (Dave Matthews not withstanding).
Solving a Problem
The Chicago River extends 156 miles. It used to flow east through the city and into Lake Michigan. That pathway took raw sewage and other pollutants away from a growing population. Unfortunately that also caused a dilemma: Chicago got all of its drinking water from the lake. Besides the awful visual image this conjures, this had the potential to become a major health issue.
So in 1887 the government developed a solution: they decided to reverse the direction of the Chicago River. This would flush their troubles away from the lake, and separate their toilet from their drinking water. Sewage would flow in the opposite direction of its natural path through the marvels of civil engineering. It would drain instead into the Des Plaines River, using a series of locks, canals, dams and pumps. Then it would travel far, far away.
A 28-mile waterway, a massive undertaking known as the Chicago Sanitary and Ship Canal, opened in 1900 to much fanfare and critical acclaim to complete this honorable mission. That is, of course, for the citizens of Chicago. I’m sure the people who lived downstream in the other direction were less thrilled.
Overcoming Topography
Engineering marvel aside, there’s another extremely interesting aspect of the local area. A low ridge runs parallel to Lake Michigan about a dozen miles west of Chicago’s lakeshore. It’s the remnants of an ancient beach. This topographic structure dates back to the end of the last ice age of 12,000 years ago. That’s all that separates two vast drainage areas: the Great Lakes / St. Lawrence basin that empties into the Atlantic Ocean and the Mississippi River basin that flows into the Gulf of Mexico.
Nowhere else is it so easy to travel between those two massive waterways. Towns grew here and became prosperous simply because of the simple portage. An early passage, the Illinois and Michigan Canal, replaced the land-based portage.
The Chicago Sanitary and Ship Canal took it one step further. It actually removed the entire Chicago River watershed from the Great Lakes drainage basin and added it to the Mississippi basin. In addition to the sanitation it provided to the city of Chicago, it served another vital purpose, the only navigable link between two hugely important commercial waterways.
The Divide
Take a look at the Google Street View image. Can you discern the slight rise? Amazingly, that is all that separates the Great Lakes from the Mississippi system.
Are you having trouble spotting it? That’s exactly the point. Contrast that with another continental divide I’ve featured previously. It quickly becomes apparent why this area on the southwest corner of Lake Michigan became so vital to trade and transportation.
This spot came to my attention from the Oak Park Tourist website. Specifically I referenced their series of pages on the Oak Park Continental Divide.
“The terrain in our Village is so flat that the slopes are difficult to perceive. The best place to see a distinct drop off in both directions is at the northwest corner of Taylor Park, at the intersection of Berkshire and Elmwood. There you will be standing on the continental divide. At the time this area was first settled, the land east of Oak Park, being an old lake bottom, was mostly swamp. Our low ridge was the first high land west of the Lake and was a desirable place to build. Thus Oak Park’s first settler, Joseph Kettlestrings, in 1837 chose to build west of Oak Park Avenue, on top of the ridge. The oak trees, growing on the sandy ridge, gave Oak Park its name.”
As a final thought, there are now pressures to re-separate to two watersheds. Some environmentalists want to return the Continental Divide to its original condition. This is for a couple of reasons. First, given the finite nature of the Great Lakes, there are concerns about the amount of water being drawn off for purposes other than drinking (i.e., as a giant toilet flushing down the Mississippi). Second, there are anxieties that linking the two large systems will hasten the spread of invasive species through even greater territories of the United States.
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