Downtown St. Paul is undergoing a transformation — and you should know what’s going on.

There’s a piece of context that’s really important here: St. Paul is drawing huge numbers of residents to its downtown core.

(Read on OR just skip to the cool/fun facts about downtown.)

The number of housing units downtown has spiked more than 20 percent in just five years — a vast majority of it market rate.

The building craze isn’t even limited to the downtown core : Projects at Seven Corners and another phase of the West Side Flats indicate the housing growth is spreading.

Even with all the residential development, rental rates jumped last year an average of more than 7 percent as apartment vacancy rates dropped below those in downtown Minneapolis.

The proof is in the, well, people: From 2010 to 2014, downtown St. Paul’s population jumped from about 6,600 to 7,900. Here’s the eye-opening part: The Metropolitan Council expects the downtown population to pass 14,000 by 2020 — that’s an 80 percent jump.

This supports a national trend: People are moving to downtown areas, especially in the Midwest. A 2015 study by the CBRE Group — one of the world’s largest real estate investment managers — found big residential jumps in the downtown cores of many major Midwestern cities over the past decade. Kansas City more than tripled. Cincinnati’s downtown doubled, and Cleveland and Columbus came close to doing the same.

Great, right? So just keep on doing what we’re doing? Not quite.

Many developers are expressing concern that residential properties — specifically apartments — are being overbuilt. And that the focus should be on bringing jobs downtown.

“Someone needs to be thinking about where do we put the next office tower in downtown St. Paul, and I don’t think anybody is thinking about that,” said Mary Bujold, president of Maxfield Research and Consulting.

St. Paul, in many ways, is testing a running theory many developers have: If you bring residents downtown, will that spur demand for retail and jobs in general?

One major downtown developer put it simply: “It’s not a growth job market. That does have an impact on rental rates, but it’s livable. There’s the state government and hospitals, but major employers are more limited.”

The city itself is pushing for retail in upcoming projects, most notably the old West Publishing site, the vacant Macy’s building and the Seven Corners Gateway site.

WHO’S BEHIND ALL THIS?

Here’s a look at some of the biggest private stakeholders in the downtown area:

James Crockarell: A Tennessee transplant, his company, Madison Equities, is now the largest building owner in downtown St. Paul. And not just in flat acreage.

He’s bullish on residential development: “The biggest motor driving the prosperity of St. Paul is housing.”

George Sherman: He’s a longtime developer who’s been focusing on residential properties in downtown St. Paul for decades — though the capital city contains only a fraction of his properties.

He noticed early in his career a major difference between St. Paul and Minneapolis when it came to development: “St. Paul spends a lot more concentrated effort on design, fitting in their master plan.”

David Brooks: Brother to famed Olympic hockey coach Herb Brooks and born on St. Paul’s East Side, he’s spent nearly a lifetime retrofitting St. Paul buildings. And he says St. Paul’s time has come.

“I love St. Paul. I’ve spent millions here. I can really feel the town, after all these 40-some years, developing.”

Ted Bigos: Chances are if you you live in downtown St. Paul, there’s a good chance you live in one of his buildings. The rental housing tycoon owns five apartment buildings boasting more than 1,300 units in the capital city’s urban center.

He says the light rail and Saints stadium have helped transform the area: “In all the years I’ve been in St. Paul, it’s never felt as good as it feels today.”

Still curious about downtown St. Paul? Of course you are.

We did a bunch of research to find out where the coolest/most expensive spots were downtown, including:

Most expensive condo (With an insane view)

The tallest building (Think you know it?)

The oldest building (Might surprise you)

Oldest bar (Probably won’t surprise you)

And the biggest, newest and most expensive properties

Dan Bauman, Sarah Horner and Tad Vezner contributed to this report.