(upbeat music begins) - [Geoffrey] They've starred in movies, they tie up traffic, they're historic.

There might be nothing more iconic than the Chicago River Bridges.

(bridge alarm blares) Let's see who makes them go up and down.

It takes a whole team to lift a bridge, but Joan Welsh has the best view.

She operates the controls three stories up in a bridge house.

(bell alarm chimes) - [Radio Voice] Go ahead, Joanie.

- I'm going to get started up here.

- [Radio Voice] Roger that.

- [Joe] Okay.

- Yeah.

- [Joe] Everybody, please be careful on the stairs.

There might be grease - [Geoffrey] While Joan prepares to open the bridge.

- Watch your step.

- [Geoffrey] Foreman, Joe Hosty, heads three stories below street level to manage the monstrous machinery that moves it.

- This is gonna come down, the bridge is going up.

It's moving like a teeter totter.

(Machinery whirs) (bridge alarm chimes) - And there it goes.

That is wild.

(upbeat music begins) At Joan's command, 1500 tons of metal and concrete make way for seven sailboats, traveling from their winter dry docks to lakefront harbors.

How long have you been doing this?

- 28 years.

- [Geoffrey] What did you do before you did this?

- That's funny, I was a cashier at Jewel.

(upbeat music continues) 10-4, bringing 18th street down.

- [Geoffrey] Joan's transition from supermarket to super-sized bridges took a year of training.

So are all the bridges identical and open the same way?

- No, very much different.

No.

Some were built in the 1800s, some in the 1900s.

(machinery clangs) That's a nice landing right there.

- That's a nice landing.

- That's what we want.

- You hear that just like, boom!

- That's what we want.

- [Geoffrey] So you're proud to be a bridge tender?

- Oh, very proud.

I was just happy to get a Chicago job at the time.

- [Geoffrey] Yeah.

- And now, all these years later, I realized what a unique, cool gem of a job I fell into.

(Geoffrey laughs) (Bridge alarm blares) - [Geoffrey] This type of bridge is called a Trunnian Bascule Bridge, and it's a big improvement over earlier bridge types.

The first river bridge, built in 1834 at Dearborn Street, was a hand cranked contraption.

It got stuck so often that a mob of angry residents demolished it.

Swing bridges that pivoted around a post in the river forced vessels to squeeze by on either side.

In 1863, the Rush Street swing bridge swung open with a herd of cattle on it.

The bridge collapsed, dumping the cows into the filthy river.

(Bridge alarm blares) Kevin Seggerson directs the roving crews who leapfrog from one bridge to another as those seven sailboats continue on their journey.

(bridge alarm blares) You're blocking traffic for like hundreds and hundreds of cars for seven sailboats.

- Sometimes one sailboat.

- So is that like some sort of federal law that boats have the right of way?

- Yes.

- Even one sailboat.

- Yes.

- [Geoffrey] For a hardworking crew trying to keep on schedule, the landmark DuSable Bridge at Michigan Avenue can be irksome because it's usually packed with shoppers and tourists.

(bridge alarm blares) - [Kevin] The operators are always yelling out the windows at this one.

- [Geoffrey] Oh really?

- Yeah, these people just don't stop here.

- [Geoffrey] They just keep walking.

- [Kevin] Yeah.

Back up!

(bridge alarm blares) - Now look at that.

They're just standing there on the bridge.

They'll get a surprise if it starts going up.

Everybody off the bridge!

(Geoffrey laughs) (bridge alarm blares) (upbeat music begins) Did you ever think you'd be doing this job?

- No.

No, but when I got it, I kind of fell in love with it.

It's one of those jobs that, when you tell people you're a bridge operator, you're doing something that not many people know.

I mean, there's 27 bridges that we operate down here.

So to be one of these people that can operate these bridges, it's kind of special.

(upbeat music continues)