Kohlsdorf: Before cars and concrete paved roads, horses carried travelers down dirt paths over the rolling hills and river valleys of Madison County.

The county's earliest bridges deteriorated quickly, due to Iowa's unrelenting winter weather.

Beginning in the 1870s, the Madison County Board of Supervisors commissioned stronger, longer lasting lattice truss bridges with protective coverings.

Lair: Our ancestors were pretty smart.

And when you build a bridge and 5 or 10 years later, you're going through the floorboards, that's not a nice way to end your trip.

And so, by covering them, they know that they would keep the floorboards much stronger and safer.

Instead of lasting 5 or 10 years, it might last 30 or 40 years.

So, the roof is a cheap insurance for the floorboards and the rest of the interior structure.

Kohlsdorf: 19 total covered bridges were constructed over the next 20 years.

More than a century later, six remain in Madison County.

Lair: Imes and Cutler-Donahoe, Roseman Bridge, Cedar Bridge, and the Holliwell Bridge.

The bridges were named after the people who live next to the bridge, and sometimes after a geographic feature, like the Hogback Bridge has the arched hill behind it.

Kohlsdorf: Over time, some bridges were relocated, while others were relieved of duty by modern counterparts.

The distinctive red and white wooden structures sat quietly, tucked into the southern Iowa farmland until 1992, when a novel written by a little-known writer from Iowa brought the bridges and the town of Winterset into the spotlight.

♪♪ Kohlsdorf: For generations, the covered bridges of Madison County were a quaint symbol of local pride and unique engineering.

Then, in an instant, the small cluster of river crossings captivated readers across the country in the 1992 romance novel, "Bridges of Madison County," written by Robert James Waller.

Lair: Well, the Roseman Bridge, of course, played the major role, and I think one of the reasons that the author really liked that is because its name is kind of romantic.

Kohlsdorf: Oprah Winfrey loved the book so much that in 1993, she brought her television show to Winterset, broadcasting on location from the Cedar Bridge.

I was so moved by this sensuous story that today, we brought our entire show to the place where this romantic affair began.

Kohlsdorf: Waller's work became one of the most popular titles of the 20th century, with 60 million copies sold.

The following year, Clint Eastwood, Meryl Streep, and a Hollywood film crew arrived to capture the famous love story for the big screen.

Lair: The Cedar Bridge was in the book, but Clint Eastwood liked the Holliwell bridge.

So, he switched out and put in the Holliwell Bridge.

So, those two covered bridges plus one of the old stone bridges were in the movie.

Kohlsdorf: The film adaptation premiered in 1995, further catapulting Winterset and its bridges into national acclaim.

I would say it was an explosion of tourists coming to the county, and kind of it's a little nostalgic about it a little romantic.

There's all sorts of feelings about the bridges.

Kohlsdorf: These cultural icons are not without controversy.

The Cedar Bridge was destroyed by arson and rebuilt twice, most recently re-opening in 2019.

Today, the bridges rarely sit empty, drawing admirers from around the world to their hallowed grounds.

The walls of each are filled with names of couples circled in hearts, as Sharpied signatures from road trippers fade into carved memorials for lost friends.

Lair: I don't think there's any other place I could be in Central Iowa and meet people from many different countries, from all over the United States.

Just last week, I had a tourist from Mexico, from Canada, from Holland.

I even had a gal fly in from Brazil because she had seen the movie, Kohlsdorf: The bridges of Madison County continue to endure as nostalgic landmarks and idyllic emblems of romance.

Travelers from around the world have made pilgrimages to this pastoral countryside to see these architectural relics up close.

The messages carved into the walls of each structure tell the stories of generations of visitors.

As the dust has settled on years gone by, the bridges are no longer asked to carry the weight of passing cars.

The shingled roofs have a new task -- now protecting the bonds of lovers, families, and friends that have left their mark on these symbolic structures.

Lair: I think there's a real romantic aura about the bridges.

A lot of second weddings or being proposed to.

There's just something romantic about that, and you look at most buildings, I mean, what's romantic about them?

But the covered bridges, I look at them, and I think they give you shelter in a blizzard, in a storm.

There's a warmth to them.

It's a safe place.

I just -- I just love them.