(suspenseful music) - [Narrator] Coming up.

- There was a real sense of danger and it was clear they had to act.

- [Narrator] The race to save a city.

- People came to Chicago trying to make a way in the world.

At the same time, it's a very dirty and gritty city.

- We used the river as our sewer.

- [Narrator] Thousands of Chicagoans were dying from wave after wave of waterborne diseases.

- You could have a healthy Chicagoan literally be dead within 24 hours.

- [Narrator] The last chance for survival was something once unthinkable... (bomb exploding) reversing the Chicago River.

- It was an innovative, imaginative, risky undertaking.

- A testimony to the ambition to make the city something better.

- [Narrator] But to save lives, others would suffer.

- What if we thought about the reversal of the Chicago River as a failure rather than a marvel, right?

- We're playing God and it changed people's lives.

- [Narrator] The Race to Reverse the River, next on Chicago Stories.

(dramatic music) (upbeat music) (water rushing) - Welcome to the glamorous part of the tour.

This is where the raw sewage that's been pumped up first comes into the plant.

- [Narrator] This is where Chicago's dirty water ends up.

- Anything that you think can fit into a manhole or a sewer will come here.

And sometimes things that you don't think of.

Bowling balls, logs, rocks, prosthetic limbs.

We've seen ID cards, one comes to mind of a gentleman from Argentina.

(turbines whirring) It takes a while to get used to the noise in this building.

(turbines whirring continues) Let me put on my safety glasses here.

- [Narrator] Using modern technologies, treatment plants like this are keeping Chicago clean.

- On an average day, we pump 1.2 billion gallons of wastewater, which is equivalent of over 2000 Olympic-sized swimming pools per day.

150 years ago, there was no treatment.

Sewage was discharged into the local rivers and streams, and ended up in Lake Michigan, the source of drinking water for the region.

- [Narrator] The Chicago River is one of the city's treasures.

(subway rumbling) This urban waterway is teeming with new life, a place to connect with the natural world in the midst of a modern metropolis.

Today's river would be almost unrecognizable to those who lived here during the 19th century when the river was treated like a sewer.

(gentle music) - The Chicago River, I think, one way we can put it is probably the city's toilet, the city's bathroom.

- We used the river as our sewer.

And whether that was human waste, industrial waste, commercial waste, anything.

- It all went into the river, and the river became very polluted.

- The water itself was not blue, not green.

It was various shades of brown.

- And the smell, we can only imagine the smell of this large sewer right through the heart of Chicago.

- [Narrator] Water from the Chicago River's north branch and south branch poured into the river's main stem flowing east through the center of the town, and emptying into Lake Michigan, the source of Chicago's drinking water.

- The river is flowing into Lake Michigan.

Where are we getting our drinking water then and now?

Lake Michigan.

- It was really water not fit for human consumption.

- [Narrator] Chicago became a town in 1833.

And from day one, it had troubles with sewage disposal and dirty water.

- We're talking about a frontier town, really a haphazard mix of houses, and stores, and stables.

Later on, dirt roads, wooden sidewalks.

It was largely a mess, livestock walking down the street.

- Not only was there no sewage treatment, there were no sewers so people would go to the bathroom in outhouses and privies.

They'd use chamber pots and perhaps, just toss it into the gutter.

And all of that would wind up in the river in one way or another.

- Public water supply didn't start until the 1840s so, prior to that, people had to use wells.

Well, that just cycled the wastewater on their own property.

- [Narrator] Chicagoans were unwittingly polluting their own well water.

Scientists hadn't yet discovered that disease was spread by microscopic organisms like bacteria found in dirty water.

- Clearly, we knew sanitation was important.

And where you didn't have good sanitation, you would see disease.

The prevailing theory of disease before germ theory was this idea of miasma, bad air, you're smelling bad air, as opposed to swallowing contaminated water.

- [Narrator] Year after year, Chicago was hit with epidemics of waterborne diseases.

One of the worst was cholera.

- Cholera is a really nasty disease.

What happens is very, very, very quickly, this bacteria starts to move through your body, and causes you to have just lots and lots of diarrhea.

And your circulatory system collapses and it's very contagious and so, you would see it move through a household, move through a neighborhood.

- [Narrator] Almost 700 Chicagoans died from cholera in the summer of 1849, that's 1 out of every 36 people.

- What was really scary about it is you could have a healthy Chicagoan and that person could get cholera and literally be dead within 24 hours.

- [Narrator] Chicago began to supply water from Lake Michigan to homes and businesses, but it only made things worse.

The untreated water was full of invisible, but deadly bacteria.

Another cholera outbreak in 1854 killed 1400 people.

Chicagoans were terrified.

Something had to be done.

Officials thought a sewer system might help rid the city of waterborne diseases, so they turned to an expert who was making a name for himself on the east coast, Ellis Sylvester Chesbrough.

- Ellis Chesbrough was a self-taught engineer.

He was a practically minded man and very dedicated for what he was doing.

- He was the type of guy who wasn't afraid of big ideas and big planning.

- [Narrator] Chesbrough was born in Maryland and started working for railroad surveyors when he was only 15.

He learned on the job and became an expert at designing railways.

Later, the city of Boston hired him to build an aqueduct.

- The public works people are always scrambling to keep ahead of the population growth.

There is just never ending work to be done.

Chicago was looking for someone to plan a sewer system, so they hired him in 1855.

- It was a growing city.

There was opportunity here.

I think people were coming here because there were problems to be solved, and they wanted to be part of it.

- [Narrator] Chesbrough surveyed the muddy streets and the filthy wastewater, and he knew he had one big problem: the city was on low-lying land.

- The city topographically was in a very undesirable place.

You wouldn't want to build a city in what was a large marsh.

The land along the river was very low, poorly drained.

So when they decided to build the sewers, you couldn't dig a trench in the ground because you would be below the river level.

- [Narrator] Chesbrough directed his workers to put sewers on top of the streets.

Then they piled on dirt, building new streets above the sewers.

But as the streets got higher, the front doors of some buildings were suddenly below street level.

Residents were perplexed, but Chesbrough wasn't finished.

- He'd come up with these ideas and they'd say, "What, you've gotta be crazy."

But it was people like him who would see a problem and be able to fix it.

- [Narrator] Chesbrough's plan was to raise the city as much as 10 feet.

Many property owners hoisted up their buildings, or hired aspiring entrepreneurs to handle the job, like the future rail car king, George Pullman.

- George Pullman was famous for raising some of the larger buildings in the downtown area.

They would circle the building with screw jacks and people would move the jack at a predetermined time, maybe a drum beat or something.

- There was like a guy in charge who would yell out, you know, "Turn, turn," and small turns incrementally so that the house wouldn't wobble, or rack and things wouldn't break.

- And so, the whole building would gradually creep up.

That was a very expensive project.

- And one by one, the city was raised, including the largest buildings.

It must have been an amazing time to to watch this happen.

- [Narrator] But some homeowners couldn't afford the expense, so they remained well below street level.

- [Michael] There's still some areas in the city where you can see this.

The streets have been raised in front of the houses to accommodate the sewers.

- [Narrator] With the ingenious Chesbrough leading the way, Chicago became the first city in the US with a comprehensively planned sewer system.

- So he was a visionary in that aspect, but he didn't quite finish that idea off because all of this sewage that was being collected, it wasn't being treated and it was being dumped right back into the river.

- There's an understanding that we are contaminating our drinking supply, even if all the science isn't quite totally solid yet.

- [Narrator] Chesbrough returned with another bold plan.

Instead of drawing water near the lake shore, where the filth from the river pooled, he wanted to build a structure called an intake crib to pull water from farther out in the lake, where it was cleaner.

- He got the idea, "we've got to put this intake way out, two miles out."

- And the reason for that is, well, if waste went into Lake Michigan, at least we could draw cleaner water in from that far away, that that waste wouldn't compromise it.

- [Narrator] To get clean water from that intake crib to the city, Chesbrough said a two-mile tunnel had to be built underneath the lake.

It was an audacious proposition.

- They literally had people digging from the land side out to the crib and from the crib side in.

- [Narrator] 60 feet below the water's surface workers constructed a tunnel under the clay lake bed.

For a year and a half, they dug around the clock using just picks and shovels.

- And then they started mining from each end toward the center.

The first shift would mine the clay out for a distance.

The second shift would come in and put timbers in that hollowed out space to support the remaining earth.

And then the third shift would come in and put masonry in place so that this was a masonry-lined tunnel.

Fortunately, they met in the middle and didn't end up with two tunnels.

It was a remarkable project for its time.

- [Narrator] The tunnel successfully connected the Lake Michigan crib to a pumping station and water tower downtown.

Chesbrough had given the city cleaner water, for the time being.

- Year after year, you're seeing some improvement, especially in cholera, but you're still seeing these large, especially typhoid outbreaks that are very much continuing through the 1850s, '60s, '70s, '80s, '90s, you know, and it was clear that these improvements were not enough to protect the water supply.

- [Narrator] In the midst of Chicago's fight against these epidemics, it faced a different sort of disaster when the Great Chicago Fire of 1871 destroyed one third of the city.

But Chicago rebuilt and kept on getting bigger.

It was the world's fastest growing city, reaching a population of half a million people by 1880.

- You see people of all races, all nationalities coming to Chicago trying to secure some level of, I think what we would call the American dream now, trying to make their way in the world.

- [Narrator] Chicago became the epicenter of innovation and industrialization.

But, as the city grew, so did pollution.

- The problem was more and more people were moving to Chicago, so there was more and more sewage being created.

On the north side, you had tanneries and glue factories pouring openly into the river.

(cows mooing) On the south side, you had the stockyards.

You had literally animal carcasses, blood, entrails pouring into the river.

- [Narrator] Meat packers dumped that animal waste into the Chicago River's most notorious stretch, a smelly inlet known as Bubbly Creek, where the water barely moved.

- You could walk across it if you wanted to.

The bubbling comes from the decomposition of the organic matter, producing methane gas and hydrogen sulfide and it's just bubbling up to the surface and smelling, and you possibly could ignite the river with all the gas.

- I just imagine these nefarious-looking bubbles kind of coming to the surface, not even thinking about the body of water as a river.

- The population was booming in Chicago and there was no way to really protect the quality of Lake Michigan water.

- [Narrator] In the 1880s, 4,000 infants died each year from diseases like typhoid.

One out of every 5 babies died before their first birthday.

- If you had water piped into your home, that actually increased the risk of under 5 mortality.

If you're very wealthy, you're gonna buy your bottled water.

You're gonna have the servants boil all of the water for you.

But unless you're in that really wealthy group, you are unwittingly putting yourself at risk of disease.

- [Narrator] Despite Chesbrough's system of drawing water from two miles offshore, Chicagoans knew there was a risk that the filth and sewage could still reach the intake.

Those fears intensified after a storm drenched the city on August 2nd, 1885.

People saw something remarkable when they looked out at Lake Michigan.

- All of this human waste and animal waste was just floating, and it was slowly making its way out closer and closer to the intake.

And I imagine there was a real panic about it.

- It could have caused a terrible epidemic had this surge of flood water carrying sewage reached the water intake crib - [Narrator] Ultimately, the wind changed direction and the tainted water narrowly missed the crib.

Disaster was averted, but residents worried that Chicago might not be so lucky next time.

- And this was really a wake-up call.

You know, we have to do something about this.

We can't put it off anymore.

It was essential for the survival of the city.

- [Narrator] There was only one option left, a truly daring proposal never accomplished before: reverse the direction of the Chicago River.

Dig a canal and send the sewage away from the lake.

Once again, many were skeptical.

Once again, they said it couldn't be done.

But the people of Chicago were determined to prove them wrong.

Geography is the key to reversing the Chicago River.

The only reason this idea was possible was because of a small ridge along the city's west edge called a subcontinental divide.

- It's a point where waters flow into two different directions.

- All of the rain and snow melt that was on the east of it would wind up back into Lake Michigan and the Great Lakes.

Everything west of it would wind up going down the Des Plaines River, the Illinois River, eventually into the Mississippi and the Gulf.

- Now the divide is very subtle.

- I have looked for it.

You know, it's not like there's a big mountain.

It's not even a hill.

It's just a very gentle rise.

- [Narrator] The idea was to build a huge canal across that subcontinental divide, allowing the Chicago River to flow backward away from Lake Michigan and into the Mississippi watershed.

It would be dug alongside a smaller canal, built half a century earlier that followed a path Native Americans had been using for generations.

- The story that I grew up with as a Potawatomi person is that this is the ancestral lands of the Potawatomi.

We had an ethos.

We still do have an ethos that we not damage the environment.

We're not given an ideology to dominate the earth, to extract from it and exploit it.

- [Narrator] Native Americans, like the Potawatomi, knew about a low, swampy spot where it was easy to cross the divide.

This spot was a portage, a place where boats could be carried across land from one river to another.

- The Chicago Portage was the intersection of the continent.

We would've used the Chicago River as the beginning point to head south and west because we'd be able to hook up again with the Mississippi River.

So we were travelers across the continent.

- [Narrator] French explorers Louis Jolliet and Jacques Marquette came through in 1673.

Many historians gave them credit for discovering the portage, a moment that's depicted by a heroic statue in Chicago's southwest suburbs.

But some Native peoples see a different story.

- I don't like it because of the narrative inferred in it.

You know, there's the heroic white people and the anonymous Indians that are, and this makes me cringe, they're dragging the canoe.

Nobody drags a canoe 'cause you'd just bust it up.

Jolliet and Marquette didn't discover anything.

They were told about the portage by the local Indians living here, and the Indians would've showed Marquette and Jolliet how to get from one place to the next.

- [Narrator] Jolliet suggested building a canal at the Chicago Portage.

He said that would make it possible to sail a ship all the way from the Great Lakes to Florida.

It would be 175 years before his idea became reality when the Illinois and Michigan Canal was completed in 1848.

- It was built for the purpose of navigation.

- It was just simply to move produce from the Mississippi River up north.

It was probably only about 6 feet deep and maybe 18 feet wide so it didn't have a whole lot of capacity.

- [Narrator] To raise money for the construction of the I&M Canal, Illinois sold off land around the Chicago River, land that the US government had purchased for pennies per acre in coercive treaties with Native Americans, including the Potawatomi.

- All of this land was stolen.

There was already this idea of manifest destiny.

Indians had to be removed west of the Mississippi and were taking the land.

Indians tried to negotiate the best deals but oftentimes, the promises were not kept.

Whatever meager promises were made, this country is founded on two essential initial sins: slavery for free labor and the taking of Indian lands, free land, essentially free land.

- [Narrator] The canal project sparked a real estate boom.

White settlers began pouring in and the little town of Chicago quickly became a city.

Three decades later, Ellis Chesbrough saw the I&M Canal as the possible solution to Chicago's water problems.

He wanted to reverse the Chicago River and make it flow south into the canal, away from the city.

- The problem was it was just so small.

- It wasn't built for drainage, it was built to float boats.

- [Narrator] The I&M Canal was deepened.

As a result, the sluggish Chicago River sometimes reversed, flowing into the canal, but only sometimes.

The canal still wasn't deep enough to keep the Chicago River running toward the Mississippi River.

- What they needed was something three times that size.

They needed something enormous.

- [Narrator] Ellis Chesbrough never got to solve this problem.

He quit his job with the city after his salary was reduced during budget cuts in 1879.

When he died seven years later, his dream of creating a new drain for Chicago's sewage was still just a dream.

But other people were pushing to make Chesbrough's vision come true.

- Ossian Guthrie, he operated the Bridgeport Pumping Station and the Bridgeport Pumping Station was built to supply water to the I&M Canal.

- [Narrator] 60-year-old Ossian Guthrie was an engineer and mechanic with a keen interest in geology and weather.

In his spare time, he took measurements of every rainfall in Chicago.

- He understood how there was a relationship between sickness and polluting the lake, and he became very vocal about it.

He would lobby legislators saying, you know, you've gotta do something about this soon because something bad is gonna happen.

I think they thought he was a crank.

City leaders knew how expensive it would be to deal with this.

I think that's why it was being fought for so long.

But there was a real sense of danger, I think, in the city.

- [Narrator] Guthrie's persistent warnings rallied civic groups to get behind Chesbrough's wild idea.

- This had to get solved and with the technology that they had at that time, this was a way to solve it.

- [Narrator] Meanwhile, Chicago was hit by the worst typhoid epidemic in its history.

Thousands were dying just as Chicago was getting set to host The World's Fair of 1893.

There was no time to waste.

- The Health Commissioner is in charge of telling the world that it is safe to come to Chicago when the world knows that Chicago is having lots and lots of problems with typhoid.

I mean, I would be very scared today of 27 million people coming to Chicago from all over the world and the potential for disease spread.

- [Narrator] A new agency called the Sanitary District of Chicago was created and officials finally put a plan in place to reverse the Chicago River.

They would build a massive new waterway called the Chicago Sanitary and Ship Canal.

It would be one of the biggest excavations in world history.

- So how could you reverse the flow?

Well, you must realize that the landform drops off.

When you get down to the city of Joliet you're 40 feet below Lake Michigan.

- The idea was to link up the south branch of the Chicago River with the Des Plaines River and to break through that subcontinental divide.

If you could dig deep enough, gravity would then pull it all away from the city.

- [Narrator] The ambitious project was kicked off on September 3rd, 1892 with a groundbreaking ceremony called Shovel Day.

- And that was held out near the Town of Lemont.

A lot of people went out there and they had a big crowd, a lot of speeches, and they dug the first shovel full of dirt to commemorate the beginning of the construction.

- [Narrator] One of the canal's architects, Lyman Cooley, addressed the crowd.

(upbeat music) - Lyman Cooley was another character like Ossian Guthrie, although he came with credentials.

He was a professor at Northwestern University and he was hired as the first chief engineer for the Sanitary District.

- So Lyman Cooley on Shovel Day, he gives this really flowery speech about how we're linking all of the region's water systems into one.

- [Narrator] Cooley argued that mankind had a divine right to build the canal saying, "Man's creative intelligence can remedy nature's caprice "joining coast, lake and river systems in one whole, "as it is not possible elsewhere on Earth."

- And this poetic verse, he kind of rhapsodized about it.

This is gonna solve all the problems for everybody.

- [Narrator] After Cooley spoke, he detonated a pile of dynamite, blowing up a mass of solid rock under the soil.

And, with that, the big dig was underway.

(dramatic music) - The canal was 28 miles long from Bridgeport to Lockport.

Fifteen miles of that goes through rock, dolomite limestone.

You would drill holes, load dynamite in the rock and boom!

And then, they would just pile the rock next to the canal.

- You know, they didn't have the sophisticated technology that we have today.

They had horses, carts, and a lot of muscle and dynamite.

- The other 13 miles was through glacial till and clay, the soils that we have in Chicago.

So that was moved by steam shovels.

(explosions booming) - You can just imagine these tremendous explosions happening and these newfangled machines that were really being developed and invented, just particularly for this project.

- [Narrator] Altogether, 42 million cubic yards were excavated.

If you piled up all of that rock and dirt in one place, it would be 13 times the size of the Great Pyramid.

The dig became a tourist attraction.

During the World's Fair in 1893, people flocked to see the excavation.

- This would never happen today, but I think it had this kind of circus-like feel where people would take the day off.

It was a spectacular thing to see because it was something that was gonna save the city, and I think everybody was getting behind it.

But also, it was just great entertainment, you know, where else are you gonna see something on this scale?

- There was a lot of excitement around this.

It was quite a spectacle at the time.

- [Narrator] But this form of entertainment was more dangerous than sightseers realized.

- There was an instance where a tourist was hit by a flying rock from one of these explosions.

- [Narrator] The rock hit 62-year-old Edgar Isbell, leaving a hole the size of an orange in his head.

He died instantly.

The canal workers faced similar dangers almost every day.

- You needed people who were willing to work 10, 11, 12 hours a day, six days a week, live in really terrible conditions.

- It was very dangerous, especially in the rock section where you were using explosives.

- There's lots of accounts of accidents, accidental setting off of dynamite, unintended explosions hurting people.

Over 250 people were killed.

- If you complained, or you got hurt, or missed work, there was always someone willing and able to take your job.

So it was a very tenuous situation for most workers at the time.

No organized labor, no protections.

- [Narrator] The majority of canal workers were European immigrants, but construction jobs were also opened up to African Americans migrating from the south.

- Those are the ones that are primarily doing the dirty work, the hard, dangerous work.

That was primarily African Americans doing that stuff.

Moving dirt, hauling bricks, digging ditches, digging trenches.

- [Narrator] At the time, less than 2% of Chicago's population was Black, but this small group played a big role.

- There was this steady stream of Black people coming to Chicago, by no stretch of imagination was it perfect, but it was a far cry from what they were experiencing in the deep south.

- [Narrator] The laborers lived and worked at the canal, sleeping in makeshift camps.

- They look like prison camps, they're just shanties.

In fact, the state sent inspectors and they said that farm animals are living better than these poor people working on the canal.

- Sometimes one camp would get into a squabble with another camp because they were different ethnic groups.

- [Narrator] Drunken and rowdy behavior was common.

- Like all human beings, you like to have fun.

And, in these camps, often fun got carried away.

The Sanitary District had to create its own police force to kind of keep control of everybody.

We look back at the work they did in a very heroic way 'cause they were saving the city.

Unfortunately, it was intense, manual labor, long days, lots of danger.

So people were doing what was necessary to get the job done and not paying a whole lot of attention to the workers' safety.

- [Narrator] As the work continued, Chicagoans were eagerly anticipating the canal's opening.

But folks downstream were dreading it.

- And if you were in St. Louis at this point in time, every sip of water you got out of the tap felt like a life gamble like, "Is this the beginning of the end for me?

"I could easily get typhoid right here, right now."

So when news came that here was possibly this new influx of waste hitting the river system for a lot of people, that was pretty terrifying to think about.

That's where the sort of immediate anger arose from.

- [Narrator] St. Louis officials filed suit against Illinois and the Sanitary District in 1899, trying to stop Chicago from sending its filth in their direction.

- So there was a very real possibility that all of their work could be stopped.

- [Narrator] Now, laborers on the ground were in a race against time.

- All that did was encourage Chicago to work faster and to open this up before they could get shut down.

And that's what happened.

- [Narrator] On January 2nd, 1900 Chicago officials realized it was now or never.

(suspenseful music) In the gray light of dawn, a small group of Sanitary District trustees dressed in suits and ties, rushed to an earthen dam near Kedzie Avenue to try to break it open.

This was the last barrier holding back the Chicago River's waters from pouring into the new canal.

- They just kind of snuck in there, fearing that an injunction could come at any minute and shut them down for years.

So it was very much a priority, on Chicago's part, to get this done as fast as possible.

- [Narrator] But the ground was frozen solid.

In desperation, officials began attacking the dam with shovels.

- And that was tough because the ground was frozen.

Even using dynamite in frozen clay wouldn't move the clay.

(dramatic music) (footsteps crunching) - There was a small panic when two men came running toward the gathering.

The trustees feared they were delivering an injunction.

(dramatic music continues) But it was just a couple of newspaper reporters who had been tipped off.

For two hours, the group tried to break through the icy ground, attracting a growing crowd of spectators.

- The contractor had to keep chipping away with his dredge, and he finally made a cut and the water flowed.

- They breached this small makeshift dam and started to let the water in.

(water flowing) - [Narrator] A great shout went up from the crowd as the dam broke open.

- I think it was a sense of relief, but it was kind of muted by this ominous threat, either from judges in Illinois or at the Supreme Court.

- [Narrator] Sanitary District officials posed for a celebratory photo and almost got swept away by the rushing water.

- And ever since the Chicago River flow has been reversed, to the benefit of the city.

- [Narrator] People in Chicago started noticing something different about the river.

- Like these stories of people just being amazed by seeing clear, transparent ice in the river.

It would've been like, "Oh my goodness, like we can do this, "like we can bring public health to this city."

- It was a miracle, you know, the river ran clear.

It was wonderful.

- The Chicago Sanitary and Ship Canal took eight years to complete and it cost $33.5 million.

Adjusted for inflation, that would be more than a billion dollars today.

- [Allison] It achieved its mission, which was to protect our lake and the water supply.

- As a result, the city becomes a much more hospitable place.

African Americans are attracted to Chicago's growth as an industrial hub.

They come here seeking jobs.

- And Chicago went from being one of the least healthy cities to one of the healthiest cities.

We cut death rates somewhere between a third to half for all of these waterborne diseases, which is pretty amazing.

- [Narrator] Missouri officials couldn't stop Chicago from opening its canal, but they still hoped to shut it down.

They took their fight all the way to the US Supreme Court.

- This was totally unprecedented in American urban history.

The idea of city's sort of causing direct effects to daily health in other places.

The Supreme Court lawsuit wasn't about the legality of the canal itself.

The case firmly focused in on the idea of waste disposal and that, ultimately, this waste was going to be causing this massive public health crisis in St. Louis.

- [Narrator] But Chicago argued that the increased flow of water was actually diluting the sewage.

- If you could divert the sewage with enough lake water, it would eventually purify itself.

Of course, St. Louis hired their experts.

- They have scientists from across the nation come and set up 14 different points along the path of the Illinois River, all the way from the canal's opening down to the St. Louis water intake.

6800 water samples from across those 14 points.

This was a massive scientific undertaking.

- [Narrator] Meanwhile, many residents in St. Louis were angry and afraid that Chicago was contaminating their water.

- Politicians came out as totally indignant.

You had these editorial cartoons of people fishing in the Mississippi River and pulling out these huge octopus-like creatures that they claimed came from Chicago.

- [Narrator] St. Louis baseball fans jeered the Windy City's National League team, giving them a new nickname.

- [Andrew] Every time the Cubs played in town for pretty much a whole year, the newspapers would actually call them the Chicago Microbes.

- [Narrator] For six years, the fight continued until 1906 when the Supreme Court ruled in favor of Chicago.

- The evidence was just too inconclusive.

How could you prove that these bacteria you found in St. Louis were the exact ones you dumped in the river 400 miles away?

- [Narrator] Justice Oliver Wendell Holmes said the canal actually seemed to be making the water cleaner downstream and fishermen were drinking water from the Illinois River, "without evil results."

- Chicago, ultimately, could not be held accountable for water conditions in St. Louis.

Just like St. Louis could not be held accountable for water conditions in Memphis, or New Orleans, or other places down river.

But, ultimately, he advised St. Louis and all other cities worried about their water, invest in a filtration system.

(chuckling) - [Narrator] Chicago had accomplished the impossible, but changing the natural world had consequences.

- It's interesting that we think about the reversal of the Chicago River as a marvel.

What if we thought about the reversal of the Chicago River as a failure rather than a marvel, right?

- Well, this is what saved Chicago.

It's what allowed Chicago to grow into this enormous city that we know and love.

But there also is this sense of sadness that we didn't think about all these other aspects that now are part of our lives.

We're playing God, and we did that, but it changed people's lives, and changed a whole ecosystem downstream.

- [Narrator] In spite of the Supreme Court ruling, the reversal of the Chicago River was causing problems in downstate Illinois.

One effect was devastating flooding.

- It doubled the size of the Illinois River.

You've got trees that are growing along the shore that are now being broken apart and falling into the river.

Everything is being just kind of submerged and consumed.

- [Narrator] Many homes and properties along the river were completely destroyed.

Hundreds of Illinois farmers sued the Sanitary District saying the flooding ravaged their crops and was putting their livelihoods at risk.

- [Michael] If you had a formerly tillable land adjacent to the river, that now was submerged it was changing a way of life very quickly for a lot of farmers who lived in that area.

- [Narrator] One lawyer argued it was, "The greatest crime "ever perpetrated in any part of this country."

- These lawsuits would be so expensive to the district that they had to fight 'em 'cause it would bankrupt the district.

We're talking about millions of dollars.

So they took it very seriously and they fought every single case.

- [Narrator] And Chicago's untreated sewage was rapidly depleting life in the Illinois River.

- The solids in the sewage began to coat everything.

The bottom was covered with this muck.

And over time, that advancing front of muck kept moving downstream.

And there were odors, you know, the people in other towns with, "Oh, that river smells."

Yeah, it's like the Chicago River used to smell.

- [Narrator] Biologists were alarmed by what they discovered.

- Around the end of the 1800s, the Illinois River Valley was one of the largest commercial fisheries within the United States.

And shortly after that peak, we saw a huge decline.

The water being sent downstate from Chicago reduced the amount of oxygen in the system, and so fish would flee the system.

- Everything our Chicago sewage touched pretty much died.

You know, you're talking about this amazing ecosystem that existed for thousands of years, just almost immediately being changed forever.

- The impact on the Illinois River was felt, and it was very severe, and it persisted for many decades.

- [Narrator] Meanwhile, at the mouth of the Chicago River, there were growing concerns.

Day after day, water was pouring in from Lake Michigan with nothing to control the flow.

Neighboring states worried that Chicago was draining the Great Lakes.

- You were drawing water out of Lake Michigan to dilute the sewage load.

The other Great Lakes states wanted to stop the diversion at Chicago.

(horn honking) - Chicago was gonna get sued again for taking too much water out of Lake Michigan.

- [Narrator] The Supreme Court put a limit on how much water Chicago could take out of the lake.

The Sanitary District needed a mechanism to control the flow.

In 1938, they built the Chicago Harbor Lock.

- The Chicago area's allowed to take 2 billion gallons a day out of Lake Michigan.

We are basically like a dam, so the lock is a way to prevent steady flow of Lake Michigan, basically to the Gulf of Mexico.

- [Announcer] Chicago (indistinct) at this time.

- [Boat Captain] That's a copy.

- [Narrator] But during heavy rainfalls, the river and canals aren't always big enough to handle all of the water.

So the gates at the mouth of the river are opened, an emergency action to prevent the city from flooding.

This allows water to flow from the river back into the lake, temporarily undoing the reversal.

- And that has occurred more frequently since the 1950s because of all the storm water that was going into the canal system.

- [Narrator] And whenever this happens, it raises fears similar to those that haunted Chicago in the 1800s.

Will sewage and pollution contaminate the lake?

- Our drinking water, the rainwater, our wastewater is all combined in the system, combined sewer system, it all comes flowing back up.

- [Narrator] To protect against flooding, a new drainage system was needed for storm water.

In 1973, the Sanitary District started digging the 17.5 billion gallon Deep Tunnel and Reservoir System and the work continues today.

- It's 109 miles of intersecting tunnels throughout the county.

It takes the overflow, or the sewer system and you have three reservoirs that hold it and then sends it back to the plant to get treated.

- [Narrator] But with bigger weather events occurring more frequently, the Deep Tunnel can't always keep up.

- The Deep Tunnel system has its benefits, right?

It has reduced flooding, but what are we going to do once the Deep Tunnel system can no longer contain and capture all of the water from more frequent rain events?

The climate crisis makes the rain events that we're experiencing here in the city more intense, which leads to more flooding.

- [Narrator] With each passing decade, the river became cleaner.

But by the early 2000s, it still wasn't considered safe for human contact.

Treatment plans had been removing organic matter from wastewater since the 1920s.

But as the 21st century began, Chicago was the only major US city that did not disinfect the bacteria in its sewage before releasing it into the rivers and canals.

That changed after 2011, when the Environmental Protection Agency ordered Chicago to begin cleaning wastewater to the highest standard, using new technology for killing germs.

- We do that at the O'Brien plant with UV rays.

Kills bacteria that's going into the river.

- We like to say we remove 97, 98% of all the impurities in it, so it is very clean.

- [Narrator] And environmental groups, like the Friends of the Chicago River, have played a key role in cleaning up the waterways.

- What Friends has been doing is to work to improve and protect the river for people, for plants, and for wildlife.

The big goal is to actually rid the river of trash completely.

So that's through policy, that's through on the ground projects and litter free removal days like today that we were out on the river collecting trash.

- [Volunteer] Yay.

- [Narrator] As the health of the water improved, so too did life in the river.

More fish began to appear.

- We've seen a huge increase in the number of species.

- [Fisherman] Aha, fish up.

- [Austin] Back in the '70s, they maybe found less than five species at any given location.

Across the whole system, somewhere around 60 to 70 species can be found.

You can catch bass, you can catch catfish that are all pretty large here.

- [Narrator] But more fish isn't always a good thing.

When the Chicago River was connected with the Mississippi River watershed, that opened a door for invasive species.

(fish splashing) Like the Asian carp.

- We have created sort of a highway for invasive species that are making their way to Lake Michigan and threatening our fish population.

- [Narrator] Experts fear what might happen if Asian carp reach Lake Michigan.

- Generally, the consensus is that it won't be great because the Great Lakes are a 7 to $8 billion fishery.

And so we don't want something to go in there, and disrupt it, and something that we can't manage.

- [Narrator] Thanks to an electrical barrier in the Sanitary and Ship Canal, Asian carp are in for a shock if they try swimming to Chicago.

- [Austin] You can actually go down there and see fish swim up and then say, "Nope," and turn back around.

- I can't believe that electric fences are going to keep them out forever.

And once they get up into the Chicago River, they'll get into the Great Lakes.

I guess our children will be eating Asian carp at dinner.

Hopefully, they're tasty.

- [Narrator] Some environmentalists say the real solution is to separate the Mississippi River Basin from the Great Lakes.

In other words, re-reverse the Chicago River.

- There's a reason why the Creator created the world as it is.

That's what we believe.

If the Creator created the Chicago River to flow into Lake Michigan, then it's meant to flow into Lake Michigan.

- We cannot think of water as waste.

We must think of it in other ways.

So if we're not centering public interest when we're asking, "Should we reverse the river," then we're gonna find ourselves with the same amount of problems just at a different scale.

- [Narrator] Re-reversing the river would be a massive project.

The Army Corps of Engineers says it could take 25 years and cost more than $18 billion to separate the watersheds.

- You can't undo the reversal, you cannot.

We're still looking at a water system that for over 100 years had raw sewage, and the stockyard blood, industrial chemicals, phosphorus, soap, glue makers, all of this as part of that muck at the bottom of the river.

The idea of allowing any of that to flow into the lake, I think would be a really great threat.

- [Narrator] What lessons does the past hold for the future?

The Chicago River was reversed out of necessity.

An ambitious and desperate undertaking to save the city from deadly epidemics of waterborne disease.

- As we go forward trying to make these decisions about what we're gonna do in the future, it's really important, I think, to kind of look back and understand just what we did.

They were just trying to keep one step ahead of death and disease.

If they had put as much thought into sewage treatment before they had reversed the river, rather than years and years after, it would've made a big difference.

- In order to make this city livable and sustainable, we've had to change the plumbing system.

- I think it played an important role in developing the city to where it is today.

- [Narrator] The river's reversal secured Chicago's future as a major metropolis.

- If it wasn't for reversing the Chicago River, we wouldn't have had these folks moving to Chicago to provide this cultural fabric that we know and love today.

- [Narrator] The reversal also reshaped the region far beyond Chicago.

- St. Louis did invest in water filtration pretty heavily in the immediate aftermath.

In 1916, St. Louis actually opened the world's largest water filtration plant at our Chain of Rocks Waterworks, which still provides much of St. Louis's drinking water today.

So I think the ultimate lesson here was that any city is mostly responsible for the conditions that it has in its immediate own backyard.

- [Narrator] More than a century after the reversal long gone are the days of treating the Chicago River as nothing more than a sewer.

- The river is transformed and you can tell when you look out an office window downtown, there's thongs of tour boats, there's a zillion kayaks.

I mean, it's just unbelievable.

- I do this for fun, but in my day job, I actually work for the Chicago Department of Public Health.

I lead architecture tours on the river and the thought of people kayaking today on that river and going down and enjoying a drink by the water, it's really something that if you look back even 20, 30 years, nobody was imagining.

- What's been done around it has really reshaped what it means to live in Chicago.

Going to walk along the Chicago River now, along the Riverwalk is something that embodies a sense of pride in Chicago.

- When I look back at that time, or think about a city going big, and saying, "There is a threat to the public health.

"It is killing people and, in the meantime, "there's something we can do about it," I would have recommended reversal, yes.

And I'm really glad that our predecessors had the courage to say, "This is gonna be hard, "but it's the right thing to do."

We've used science, we've used engineering.

And then, to see that drop off in death, we really did something for this city and its ability to grow.

You've gotta do big things to get big things done in public health.