Duluth's Aerial Lift Bridge is celebrating its 120th birthday this year. It helps manage the farthest inland port in the world.

"It's like the best, little daytrip from the cities, I think," said Hannah Foss, who was visiting Duluth.

The city has a way of attracting visitors from near and far, thanks in large part to its port.

"We've got ships from all over the world. We have two ships right now that are picking up grain and heading back across the ocean," said bridge supervisor Dave Campbell.

And as they head for the high seas, they'll see a sight and hear a sound most ship captains have grown used to.

The bridge has been granting safe passage for so long that it's become part of the city's skyline. It's evolved over the years, but many of its original parts are still intact.

"First one was built in 1905. That's what they call a gondola bridge, or transporter bridge," said Campbell. "In 1929, traffic got to be so much on and off the bridge, they started construction on what we have here."

In the history of the bridge, Campbell is just the 10th supervisor. He's been here so long he can sense a problem just by listening and make a fix. There are backups for just about every part.

"For example, there was a small ping while it was raising, so we need to find out what's going on with that before that ping becomes a bang," said Campbell.

On average, the bridge lifts about 4,000 times a year. And when the really big ships come through, it will rise 135 feet above the water.

It takes three minutes for the bridge to go up, and three minutes to come down. Cables and counterweights make it all happen by moving the lift span, which weighs about 1,000 tons.

While ships and boats go under, cars and trucks go over. And all of it is controlled in a pilot house that's located on the bridge.

"Ours is unique in that we ride with the bridge as it raises up," said Campbell. "We control our traffic lights from here."

This is where things can get pretty wild. When you are the catalyst for commerce, some days are downright stressful.

"There are boats wanting to go out. Boats wanting to come in. There's a laker coming across the lake," said Campbell.

Multi-tasking, while making sure people don't jump onto the bridge while it's on the move.

No matter what the season or the weather, the operators are on watch, 24-7. Like ships in the night, they rarely meet the captains and their crews, but they always have their back.

"We know it's a very cool job. It's one that not many people have had," said Campbell. "It's nice to see people who are excited to see the bridge and see the boats."

The Aerial Lift Bridge is on the National Register of Historic Places. The only time it doesn't lift is from mid-January to mid-March, during the shipping offseason.

However, it closed for three days in December 2019 because 80,000 pounds of ice were packed on the bridge during a winter storm.