- Look at this view.

How would you like to wake up to that?

That is the Rock Island Passage; that's why we're here.

[upbeat music] - You know what I mean?

Look at this, look at this.

- There's so many great books here.

- Hey, have you worn any epaulets lately?

I mean, I think it's a fashion style.

We need to bring that back.

Oh, here we go, all right.

Well, I mean, we can look at this.

[hosts talking over each other] [keyboard clicking] - Nick: All right, yeah, that's pretty cool.

Whoa, whoa, whoa, wait, wait.

Where did Cat go?

- Cat: Time to get some peace and quiet.

Apparently, being a lighthouse keeper was one of the more remote and isolated jobs in history.

So I'm off to check out the site of Wisconsin's oldest lighthouse, the Pottawatomie Lighthouse on Rock Island.

We'll see if it's as quiet as I'm hoping.

The journey will take me up to the very end of Door County and into Lake Michigan, one of the Great Lakes.

The Great Lakes refers to Lakes Michigan, Superior, Huron, Ontario, and Erie.

These lakes and their connecting channels make up the planet's largest surface freshwater system.

They contain just over 20% of the world's surface fresh water.

People began settling in the western Great Lakes region, including parts of what is now Wisconsin, over 10,000 years ago.

- Jeanell Dailey: Good morning!

- Morning!

Welcome to the Pottawatomie Lighthouse.

- Paul Dailey: Morning.

- Cat: Hi.

- I'm Jeanell.

- Cat: Hi.

- I'm Paul.

- Hi, I'm Cat.

Could I take a look inside?

- Sure.

- Oh, sure, we'd love to show you!

- So tell me, why was this lighthouse built here?

- Okay, if you want to get from Lake Michigan to Green Bay, you have to find a passage through these islands.

The best passage is the Rock Island Passage.

It's deeper, it's wider, and it made most sense to put a light here.

And the great thing is that once you come to Lake Michigan and you come to this area where we are, come down to Green Bay, get onto the Fox River, go to Portage.

From there, onto the Wisconsin, to the Mississippi River, and at that point, you've basically opened up the interior of the country.

And so this route was heavily used, primarily for the fur trade, but later for things like forestry.

There was also lead mining in the southwest of the state.

But this area that we are right now was extremely well-traveled in those times.

- Cat: The original Pottawatomie Lighthouse was the first to be built in the area that is now Wisconsin.

Merchants from Detroit petitioned Congress for a light on Rock Island starting in 1832.

After approval by Congress, construction on the original lighthouse began in 1836 and was completed in October of 1837.

The first keeper, David E. Corbin, started that December.

Unfortunately, the original lighthouse wasn't the best quality.

The structure was already starting to fall apart by the early 1840s, and by 1858, things were so bad that the original buildings were demolished and a new tower and house were constructed in their place.

But you can still see the remains of the original structure in this photo from 1883.

- So we are now standing in the house that was built in 1858.

There's a couple things that I'll point out.

First of all, we have a very important set of four beams.

One, two, three, and four.

And these beams start down in the cellar, and they go up and support the lantern room at the top of the building.

This is rather unusual to have a big door in your bedroom.

Well, I'm sure it saved them lots of stairs, climbing up and down to see how well the lantern was burning at night.

Also, look at this view.

How would you like to wake up to that?

That is the Rock Island Passage; that's why we're here.

- Cat: In 1994, Friends of Rock Island State Park began work on restoring Pottawatomie Lighthouse.

In 2004, the lighthouse was dedicated as a museum.

It was restored to resemble its appearance in the early 1900s.

If I'm trying to imagine what the life of lighthouse keepers was like, what was the day-to-day life like for them?

- Probably pretty similar to our days.

We get up, we have our breakfast, and then clean.

Of course, they would have the other end of the day also to really jump into action, when they had to have kerosene in the lantern, make sure the wick is the proper length, periodically check to make sure the light is strong.

- The keepers wore many hats.

The supply boat did bring some food, but early on, that was sometimes unreliable.

And so a big part of their life was just the simple fact of procuring food.

And old photographs show rather extensive gardens here.

There was a rigorous schedule of all the maintenance.

Everything.

And not just the light, but they expected the whole facility to be spick-and-span.

And the work was very hard and they were in an isolated place, and they had to make do with what they had.

This is a copy of the lighthouse keeper's journal for this lighthouse.

So you can literally flip back to a particular day, maybe 100 years ago, and see was going on here in this lighthouse.

- Well, that is so cool 'cause I've been writing my own logbook.

What kind of things would the keepers log in their books?

- Mostly, day to day, it was things like weather.

If boats were coming through, they would try to identify them.

It gives us a nice slice and a good view into the history of the lighthouse.

This is a small scale model of a Fresnel lens.

And basically, a Fresnel lens is just many, many, many prisms of glass arranged so as to greatly multiply the light that goes out.

But the basic idea is that you have some sort of lamp or light, and it is inside the lamp, the lens, and it multiplies all of that light and sends it out so the ships can see it.

- Cat: The Fresnel lens, whose design is credited to the French physicist Augustin-Jean Fresnel around 1820, uses multiple prisms and lenses to gather and focus light, creating a very efficient and intense beam.

By the end of the 1850s, almost all lighthouses in the U.S. were using Fresnel lenses.

The biggest Fresnel lenses in lighthouses could be over 12 feet tall and weigh over 15,000 pounds!

When the Pottawatomie Lighthouse was first built in the 1830s, it didn't have a Fresnel lens, but one was installed when the structure was rebuilt in the 1850s.

- Well, here we are in the lantern room, where everyone wants to go.

This is a replica of a fourth-order Fresnel lens, which would've projected the light out onto the Rock Island Passage.

But if we're looking out here, you can see St. Martin Island, and behind St. Martin Island is Upper Michigan Garden Peninsula.

- Cat: I learned so much at the Pottawatomie Lighthouse, and it was super quiet and peaceful.

But now, I have even more questions.

Like why was Door County so important for maritime history, and where can I learn more about how ships navigated hundreds of years ago?

Time to make another stop.

This time, at the Door County Maritime Museum to see if I can get some answers.

What is special about this particular place?

- Sam Perlman: This little peninsula has had a global impact going back to the first European traders who were coming here, buying furs from the Native populations, shipping those back to Europe, all the way through World War II, when the shipyards of Sturgeon Bay were launching a new vessel every five days, right up until today's tourists, who come and want to boat or eat the whitefish that comes out of Lake Michigan.

And so we want to just reinforce that this is truly a maritime community, and all of Door County's history is maritime history.

- Kevin Osgood: We are on the seventh floor of the Jim Kress Maritime Lighthouse Tower.

This is the floor that focuses on navigation, and it starts with what First Nations did to navigate around here, what the Europeans brought when they arrived, on up to modern navigation of today.

It's all profiled on this floor.

- What's your favorite part?

- I think my favorite part, our researcher as we were developing all of these exhibits, found maps and charts going all the way back to 1612.

And to see the development of those mapping technologies over the centuries is really fantastic.

You remember that these Europeans would come here, they would use the rough mapping skills that they had.

Then they would take that information back to Europe, give it to a map maker, who would then use some, let's call it artistic license to draw a map.

So you see over the time, the differences in how they were able to portray the Great Lakes.

- Behind you is the very first nautical chart of the bay of Green Bay from 1845.

North is on the right, not at the top.

And the only places they knew depth in the water was where the ships had been.

- Hey, where'd everyone go?

Oh, well.

Lighthouses like the Pottawatomie played a key role in helping ships navigate the Great Lakes.

Thanks to the hard and often lonely work of lighthouse keepers and their assistants, the waterways of this area were connected to the entire globe.

If you live near the Great Lakes or another body of water, see if you can find the lighthouse that's closest to you, or try exploring more of lighthouse history.

What's the oldest lighthouse in the United States?

What's the tallest?

And remember that the history of water transport is everyone's history.

- Where did Cat go?

- Eh.

- She left her phone though.

Let's get into her bank account.

[all laughing] [ship crashing] [Sam laughing] - Your ship has been lost to the storm.

- Oh, no!