At 2429 W. University Av. stands a square, two-story brick structure, with minimal decorations. It was built in 1909 to print the Twin City Commercial Bulletin, a retail trade journal.

Few who pass would give it any thought, except for one detail: the stone letters MINNEAPOLIS on the left side of the building, and SAINT PAUL on the right.

You can’t help but think it straddles the border. What would that be like? If St. Paul police arrived to arrest you, could you run to the Minneapolis side? Is there a dotted line down the middle of the staircase? Whatever the story, you’re glad it’s there to tell you when you’ve left one city and entered the other.

Except it’s not really on the border.

Look it up on Google Map Street View: No boundary line says Minneapolis over here, St. Paul over there. Street View says “Minneapolis” at the SuperAmerica on Bedford Avenue, and “St. Paul” right in front of Hubbard Broadcasting’s big red KSTP letters. In between it just says “University Avenue, Minnesota, USA.”

As if it belongs to no city at all, and both at once.

Some streets are destinations: Hennepin. Some are showplaces: Summit. Every town has a University Avenue, a practical road with unlovely expanses, small treasures, lost stories, a great silent chorus of history bound up in the bricks. A working street.

But not every town has one that draws a broad line between two downtowns, bearing the same name at each end. A newcomer sitting in the Green Line train when it begins traversing this route next Saturday could easily see the sights outside the window as a long, plotless movie, just another old street past its prime, due for a juice of transit mojo. Easy, and wrong.

It was always a street that took the temperature of our urban health. Let’s look back and hear what it says about where we were, and where this new train might be taking us.

A journey down University Avenue is a trip back in time, but it’s a jittery jump from one decade to another, often in the same block.

If the original plan had been followed, it would be located to the north, tying the University of Minnesota to Hamline University.

All together now: That’s why it’s called University. Makes sense, no? But this grand idea was thwarted by construction of some rail yards near the U, so the name was bestowed on the artery we call University today.

Just another street at first, there were grand plans for an elegant, broad boulevard tying the towns together in urbane perfection.

Didn’t happen. Rarely does. It grew up without a plan, a stretch of road more useful than beautiful, the route of the Twin Cities’ first inter-urban trolley. Its sole purpose for most people: to get you from here to there.

But along the way were a thousand reasons to stop.

Take your time, see the sights

Some reports say the new train will take nearly an hour to get from downtown Minneapolis to downtown St. Paul, but that’s not all bad. You’ll have time to look out the window and study how the decades knit themselves together in a long braid of brick and glass.

A postwar drive-in, the remnants of a 1970s Embers, a World War I-era factory. Near Hwy. 280 stands the old International Harvester assembly building from 1915 — once a place where tractors were put together, now offices. Move east: new residential units in the Chittenden and Eastman building, decorated in the style of Louis Sullivan.

Keep going. There’s a nondescript structure devoted to architectural antiques, a cupcake restaurant, a youth arts school upstairs. It’s a maze inside, with old fire doors bearing the name of a long-gone manufacturer. You fear it will be improved, its tenants driven out for cheaper digs.

Same with Ax-Man, a surplus store that thrives in old mixed-commercial neighborhoods and is less popular when nice condos go up and people think, “I don’t need 40 screwdrivers. I need a Whole Foods.” But it’s a fixture; that could never happen.

Porky’s was a fixture, too. But we’ll get to that.

The enormous Menards holds down the site once occupied by the Twins Motor Inn, which dueled for customers with the Midway Motor Inn across the street for decades — and lost. Habitat for Humanity has a solemn new building on the site of an old low-slung commercial property with apartments upstairs. Just the kind of common building that often gets torn down, because, heck, we’ve got so many. Until they’re all gone.

Snelling: If the train stops and you have a window seat, you might see a jewel-box bank building, an embassy for the “Mad Men” era. The big green beast on the southwest corner is Spruce Tree Center, which replaced a modest 1920s-era drugstore. North across Snelling is a CVS drugstore, which looks like it could be anywhere; it replaced a curious circular building intended to look like a tree, the corporate symbol of Midwest Federal. Holding down the northeast corner is a used-book shop in a structure that wouldn’t have looked out of place at the 1939 World’s Fair.

Move along, heading east: The astonishing edifice of terra cotta with the proud tall tower, right after you pass Snelling? What, you don’t see anything? Right. Pity. The Montgomery Ward building, one of the largest ever built in St. Paul, was torn down in 1995 because someone looked at that and thought “can’t possibly imagine any use for a grand historic structure. No, this area needs a low-slung strip mall indistinguishable from the worst suburban cliché.” And so it got one.

Midway Center once was home to the Snelling streetcar repair facility. Any remnant ghosts may be pleased to see trains sliding past again.

Move along. The forbidding structure with the thin-finger clock tower was a casket factory. If it’s ever made over into residential lofts, perhaps “Kasquette @ University” would be a good name. You might not notice the Brown & Bigelow building, home to a firm that flooded the country with millions of promotional pieces. Norman Rockwell Boy Scout calendars, Maxfield Parrish posters, pin-up stuff for garages and barbershops. The famous scene of dogs playing poker was a B&B image.

Demolition time

The Dale Street intersection offers few clues to its randy past. A big stolid structure replaced the Faust theater — sorry, the Notorious Faust, as it was known. In the bad old days the once-venerable neighborhood movie house where the kiddies saw serials on Saturdays turned into a sticky-floored porn house for the raincoat crowd, attracting clientele who couldn’t get triple-X fare in their own part of town. Add smut-mag shops. Add peep shows. Add neighbors’ complaints of prostitution and drug dealing on the street corner outside. It didn’t help that it was named after a man who made a deal with the devil.

The city spent almost $2 million to buy the Faust block and demolish it in 1995. This might be where someone says, “University was more interesting back then,” and in the sense that scum and decay can be interesting, sure. You might wish the 1930s makeover by the marvelous Minnesota movie theater architects, Liebenberg and Kaplan, designers of the Uptown, had survived to be repurposed into a neighborhood performing arts center. But you get the sense the locals didn’t just want that building demolished. They wanted to salt the earth.

More changes on the way

The Green Line changes the character of University the same way it was altered for cars. What was once a wide river of traffic with autos parked like boats tied to the shore now feels like a tightly channeled stream. If it occurs to you to stop and park, you realize you can’t, for the most part.

Change has its price. Rents rise, and stores that incubated immigrant businesses will find new purposes. The Asian grocery that serves the neighborhood is replaced by a chic Asian restaurant that serves the outsiders. Block after block will be unrecognizable in a decade or so.

You’ll have to tell newcomers what it was like: cheap bars, burnt-out neon, gloomy buildings with mysterious tenants, storefront signs in different languages, buses trundling up and down like a parade of rheumatic elephants — a messy stretch, but practical as well-worn work boots.

Now and then it came to life like no other street in town, which brings us back to Porky’s. You could say the late Porky’s was the repository of the avenue’s soul, at least its postwar version. It wasn’t just the sign, with the jaunty top-hatted pig; it wasn’t just the bygone vibe of the drive-in. Classic cars gathered there to revive the Era of Cruising, and when the old-car show was in town it was like the 1950s had been reincarnated in sheet metal and chrome, loudly prowling up and down the avenue as if they owned the street. Which they did, in a way.

But the train owns the avenue now.