Katie Muehe, who travels every workday from her home in St. Paul to her job in Minneapolis, has a surefire way of keeping track of which city she's in.

"If my drink doesn't come with a little umbrella, I'm in St. Paul," she chuckled.

Longtime arch rivals with distinct personalities, the Twin Cities are now showing signs that the walls dividing them are crumbling and that, as residents, we are increasingly seeing ourselves the way the rest of the world sees us: not as two individual cities but as a single metropolitan area.

We cross the Mississippi River to go to Twins games at Target Field and Wild games at the Xcel. We go to the Guthrie and the Ordway, to the Institute of Arts and the Science Museum, to Walker Art Center and the History Center. The Minneapolis and St. Paul YMCAs -- separate entities for the past 150 years -- are merging at the end of this year.

And, like Muehe, an ever-growing number of us live in one city and work in the other, a pattern that is likely to increase when the light-rail line connects the two downtowns in 2014.

Does all of this mean that the border between the cities is blurring? Definitely, says Todd Klingel, president of the Minneapolis Regional Chamber of Commerce. "Certainly, things like the Twins and Wild [playing in different cities] help, but we need for these borders to keep evaporating if we're going to compete in a national marketplace," he said.

In vying for everything from businesses to tourists, other large cities are widening their focus to encompass their entire metro areas.

"We're competing with other regions" instead of other cities, Klingel said. "We all need to cooperate if we're going to take full advantage of the marketplace. Our best selling point is the strength of the group."

Working together instead of competing also produces efficiencies, a theory behind the formation of a number of metrowide agencies ranging from the Metropolitan Council to the recently launched economic development group Greater MSP.

Allegiances are being blurred further by population patterns. The vast majority of those who call themselves Twin Citians don't, in fact, live in Minneapolis or St. Paul. As of the 2010 census, the two cities have a combined population of just under 700,000, a number dwarfed by the 2.5 million people who live in the surrounding suburbs.

On the whole, younger residents are less concerned about the borders. Two years ago when Leora Maccabee launched an online magazine aimed at Jews under 30 (www.tcjewfolk.com), she considered having separate focuses on Minneapolis and St. Paul. But the St. Paul native decided that it wasn't necessary.

"People my generation don't think that way," said Maccabee, now 28.

Muehe, who is 25 and crosses the city line without a second thought, reinforced that notion. "It's not like: 'Oh, my gosh, I've crossed the river! I'm in a different place now.'"

Many older residents of both cities tend to cling to longtime stereotypes that St. Paul is primarily Irish and Minneapolis is more Scandinavian. But in fact, according to the most recent demographic studies, German ancestry is No. 1 in both places.

RNC started it all

The new cooperative attitude was highlighted most visibly when St. Paul Mayor Chris Coleman and Minneapolis Mayor R.T. Rybak joined forces to woo the 2008 Republican National Convention to the Xcel Energy Center. That cooperation continues, most recently in June when the mayors shared a bicycle ride from Minneapolis to St. Paul to promote the expansion of the Nice Ride bike program.

But all this collaboration doesn't mean that a merger between the towns is imminent -- or, for that matter, even likely.

John Mannillo, a longtime St. Paul booster, says he's all for cooperation if it's good for business. "Some things just make good economic sense," he said.

But Mannillo, who describes himself as a "redeveloper" ("I don't tear down old buildings; I fix them up"), said that in the long run, St. Paulites also need to protect their unique interests. He's adamant that his city will never be absorbed by its bigger neighbor to the west.

"I think the people in Minneapolis would be OK with that, but it wouldn't go over in St. Paul," he said. "If there are economic reasons, like there seem to be with the Y, then I can see it. But when that happens, it takes something away from who we are. The people in St. Paul have to stand up and protect our identity."

There is an ironic symmetry to the fact that economics is pulling the two cities together, because that's what drove them apart in the first place. As the two biggest communities on the northern end of the Mississippi River, Minneapolis and St. Paul spent the last half of the 1800s jostling for the chance to control the shipping trade and, later, hydroelectric power.

The rivalry's first major truce came in 1961 when both cities agreed to drop their separate minor-league baseball teams and unite behind the Minnesota Twins. Still, there were limits on the cooperation; a decade after the team's arrival, people riding the bus from one city to the other still had to pay an additional fare to cross the city line.

More recently, the two towns often behaved like the siblings after which they were named, trading smart-alecky snipes. Star Tribune sports columnist Sid Hartman would refer to St. Paul as "East Berlin," and the late Rod Maddox, the quintessential St. Paul booster best known for launching the Taste of Minnesota, would joke about needing to get an inoculation before crossing the border.

Keeping things balanced

Amber Collett, who has lived and worked in both cities, agrees that "some people are fiercely loyal to their city." But she doesn't think that loyalty and cooperation are mutually exclusive.

As an event planner for Bike Walk Twin Cities, a nonprofit organization that promotes biking and walking across the entire metro area, she focuses on ways to get people on both sides of the river to work together without feeling that they've compromised their uniqueness.

"Whenever we host an event, we make sure that both cities are represented," she said. "There probably will always be a division between the two cities, but I think they are getting more alike all the time."

Part of that is a result of the franchising that has become prominent in business. Long gone are the days when the two downtowns were home to different stores and restaurants. These days, not only do they feature mostly the same shopping, but it's not much different from what's available in suburban malls.

As a result, even though the downtowns have unique auras, many people are starting to look at them as different neighborhoods rather than separate cities.

"It's the way Grand Avenue is different from Uptown," Muehe said. "Both have great restaurants, but Minneapolis is a little flashier, while St. Paul is more into draft beers."

Collett's decision to move between cities had nothing to do with the big picture of whose border she was within.

"That wasn't the case at all," she said. "For me, it's all about neighborhoods. Both cities have so many great neighborhoods. Each stage of my life has needed a different kind of neighborhood. I was just looking for a change."

Jeff Strickler • 612-673-7392