The Northern Avenue Bridge has suffered the slings and arrows of the city’s shifting fortunes for more than a century — and it’s always come out swinging. Today, a growing chorus of voices is calling for it to go the way of New York’s Penn Station or Boston’s own West End.

For a city swimming in history and trying not to drown in it, decisions over what to keep and what to bulldoze in the name of progress are always complicated. Consider a flyer still posted on one of the bridge’s columns: “Join the crusade to save the bridge today’’ reads the notice from 2000.

Greg Galer, executive director of the Boston Preservation Alliance, took me on a tour of the rusting behemoth and made the case that destroying the bridge would be squandering a cultural treasure.

Below is an edited excerpt:

What’s so historic about this bridge?

It is about a century old and typical of the time. It’s a rare survivor. There aren’t many swing bridges left in the state or in the country, particularly on this scale. The middle span is 283 feet long, which makes it a monster for the time. Ships used to go up and down the Fort Point Channel frequently, and a railroad went over the bridge. Multimodal transport is not a new idea, nor are mixed-use areas. We’re rediscovering those things now as we’ve re-embraced urban living, but we’re not reinventing the wheel.

Has it deteriorated too much to save?

This bridge is sadly typical of American infrastructure, which is suffering from a lack of care and maintenance. If you don’t paint and maintain these things, they rust and deteriorate, particularly over salt water. What we’re standing in front of now is the result of decades and decades of neglect. But listen, we’re not fanatic preservationists. We don’t want to keep every bolt. The deck is all rotted out, that has to go. A lot of the undersiding needs to be replaced, no question. But the essence of this bridge, this industrial structure and its functionality, needs to be saved. Look at New York City — what if, in the name of progress, they’d torn down that rusting hulk that’s today the High Line? This could be our own little High Line. We’re whittling away at Boston’s historic fabric, and the industrial and transportation legacy in particular.

Yet there are lots of reclaimed old industrial structures that we’ve reclaimed in the Seaport District, particularly old factories that had been converted to residential or commercial space.

Exactly. But we forget that there was a huge fight to save the Fort Point historic district as well. We heard the same arguments then: Bulldoze these old factories and build the newest, most modern structures and amenities. We fought that fiercely, and look how successful and attractive that neighborhood is today. People are attracted to a mixture of old and new, as long as it is functional.

The navigation issue is key here, and part of the reason the Coast Guard and the Army Corps of Engineers want the bridge removed. Is the bridge a hazard?

The swing span, which enables water traffic, was originally designed to run using compressed air. In the bridge tender’s house, the equipment — compressors and tanks — is still there. When it ran on air, the bridge operated much more smoothly and swiftly than it does now, with an awkward electric motor. The motor wasn’t designed to move a bridge like this. People complain now that it takes forever for the bridge to open, that it is such a pain. Well, yes, since we’ve let the original mechanisms rot, it now runs on bubblegum and duct tape. They might as well have a gerbil running on a wheel. Add to that the bad condition of the span and of course we turn it slowly for fear it will fall apart. But if we got it back to the way it was designed to run, it would be the epitome of steampunk. People need to forget what this bridge is today and envision what it was.

Is this is the price of progress, with GE coming to town?

GE is a company with an industrial past. What a better way to rehab the bridge than to use some nice, new GE motors to drive it, with new lighting, with cafes. That would be a perfect next chapter in this bridge’s story. History is about place-making. And this could be a place. It could be something where the bridge — all lit up with GE bulbs — swings open every hour and people come down here with a bottle of wine and meet up and watch it. To say this is just about crossing a river is to sell this place short.

It is money either way, to replace or rebuild. Is it worth the cost to rehab?

Yes, the cheapest thing to do would be to build another Moakley Bridge, designed for cars, that goes up and over, and is boring and bland. But if you go down the list of things that people are looking for in a bridge — flat for walking and biking, full of character, connected to the city and its history, a cultural destination, and able to allow navigation — the bridge we have already does all those things. Why should we go through the aggravation of coming up with something new, when we can fix what we have; it would be just as expensive.

Speaking of construction, there’s a real workmanlike anonymity to these industrial structures.

This bridge was designed by a city employee, no one famous. It was assembled by guys with hot rivets and pneumatic hammers, fastening each bolt one-by-one. Our infrastructure used to be thought of differently, people were proud of it. Look at utilitarian buildings like the gorgeous Chestnut Hill Waterworks — that was just a pumping station. Now we always go for the cheapest option, but smart engineering design has a beauty of its own. Steampunk is popular for a reason; there’s a beauty in the simplicity and functionality of industrial design.

This fight has been going on for a long time. Have we reached the end, one way or another?

There’s a reason why this bridge is still here. It means something to Bostonians. There’s a constituency for it, and that’s why the city has kept the preservation option on the table. The real threat now comes from the Army Corps of Engineers and the Coast Guard. We feel that’s federal overreach on their part, forcing the city to do more than is required. The Army Corps hasn’t liked this bridge for a long time; they’d be happy to see it gone. They’re trying to stomp on our rights as a city.

Are you making a state’s-right argument for this bridge?

I am to a certain degree, which is rare for me. But in this case, the bad guy isn’t necessarily the city, but the feds. My beef is with the Corps and the Coast Guard. That said, it is nice to see so many people again paying attention to this issue. Dialogue is good.

Alex Kingsbury can be reached at alex.kingsbury@globe.com.