On a Sunday afternoon in late December, Elna Baker stood in front of a class of around 20 young men in ties and women in skirts. Ms. Baker, who is 25 and has red hair and a bright red vintage coat, was wearing a plaid miniskirt, a black turtleneck sweater and black suede high heels. These shoes had replaced the black low-top Converse she had been wearing earlier, before she stepped through the threshold of the Union Square ward of the Church of Jesus Christ of Latter-Day Saints.

Ms. Baker, who has never been married, teaches a Marriage Prep class every week at her church. The day The Observer visited, her class was supposed to be focusing on what to do when you and your spouse get into a fight, but she had agreed to turn the class over to discussing how her students felt about the spotlight Mormonism has been placed under recently. Or as Ms. Baker put it, “I’m supposed to be talking about what you would do with your hypothetical spouse when you get into a hypothetical fight,” since none of the people she was talking to were married either.

Ms. Baker is a member of the Union Square “singles’ ward,” for church members ages 18 to 30, and every Sunday its 240 or so members show up for three hours—an hour of a more or less traditional church ceremony from 11 a.m. to noon, a mixed-gender class from noon until 1 p.m. and a single-gender class from 1 p.m. to 2 p.m. The Mormon church has no paid clergy or teachers, and so members like Ms. Baker are assigned volunteer tasks by the ward’s bishop.

New York used to be a spiritual Babylon for the world’s 12 million Mormons; theirs was a religion more at home in the West (the church is headquartered in Salt Lake City), with its pioneer ethos and its libertarian leanings and its divorce from the East Coast political, social and religious establishment. Still, Mormons’ numbers in Manhattan have increased by about 50 percent in the past 10 years, though overall they remain a tiny percentage of the population—the community has gone from 3,225 practicing Mormons in December 1997 to 4,853 by the end of September 2007, according to figures supplied by a church spokesman. The numbers are probably relatively low because the church still has trouble converting New Yorkers—the growth is “not all organic,” said newly installed stake president David Buckner. (A Mormon “stake” is roughly like a Catholic diocese.) “Many people have moved in—transplants from the suburbs, or people did Wall Street internships and stayed.”

The church service I attended with Ms. Baker during the first hour was billed as a special holiday service, and it turned out to be part talent show (three women doing a warbly rendition of “Away in a Manger” ); part what Ms. Baker referred to as “kind of chicken-soup-for-the-soul moments” when congregation members “gave testimony”; and part religious observance (Mormons, like Catholics, take the sacrament, but with water instead of wine), with hymns from a Mormon hymnal.

When she’s not in church, Ms. Baker is a stand-up comedian and a hostess at Nobu. “I don’t want to be pegged as the Mormon comedian, or to be known for telling jokes for a religion that’s not that funny—it’s kind of a one-trick pony,” Ms. Baker said earlier that week by phone. “And yet, if I don’t include the fact that I’m Mormon, it’s almost like it doesn’t quite make sense. Why is the character making these choices?

“I think that everyone chooses to believe I’m their token ‘normal’ Mormon,” she continued. “In their minds, Mormons are still weird and crazy and I’m the only normal one. Everything that ever happens about Mormons, no matter where I am in life, I become the authority.”

But in a city like New York, the very existence of a thriving community of “normal” Mormons is almost head-scratching. Isn’t New York supposed to be a mecca for weirdos and drunks and late-night clubgoers and artists? Besides, aren’t there too many, you know, temptations here for Mormons, who, thanks to a code of beliefs called the Word of Wisdom, do not drink alcohol or caffeine, or do drugs, or have premarital sex (or any kind of premarital sexual anything beyond kissing)?

Apparently not. If there’s one theme you hear over and over again from young Mormons, it’s that the Word of Wisdom ultimately gives them a leg up in the ultra-competitive New York business world—they’re never hung over, after all, and they never have to worry about STDs or being pregnant or blacking out and knocking their teeth out. “I think it’s exciting to be in New York and experience the city in a more wholesome manner because I’m Mormon,” said Colin Wheeler, 30, who recently moved to Manhattan from Sacramento and works for the CW network’s morning show. “This city would be very cold and very lonely and very depressing if I wasn’t Mormon.”

“I like having rules that define my morality,” said Kieran, a flight attendant in Ms. Baker’s Marriage Prep class. She had dyed blond hair and was wearing a low-cut blue dress. “I need moral guidelines.”

Of course, there are other religions that subscribe to some or all of these tenets, but they’re usually sequestered in their own little communities—they’re not among us in the way that Mormons are—and the clothing they wear almost immediately identifies them as members of a conservative religion.

Mormons, however, wear their secret garments underneath their clothes, so really, they look just like everyone else, just a little more clean-cut. (Most Mormons who have gotten a temple “recommend”—confirmation from their bishop that they’re living a pure, Mormon life—wear the so-called garments, which are basically an undershirt and shorts. Mormons consider garments sacred and generally do not discuss them with outsiders, though their design is now readily available on the Internet.) And that’s a big part of Mormonism, too: to go out into the world and “make a difference,” which also means converting people, and so looking and acting pretty much like everyone else and engaging with them is part of the deal.

Steven Fales, a gay ex-Mormon who wrote and starred in an Off Broadway play Confessions of a Mormon Boy, and who has lived in New York for over a decade, explained that Mormons “see New York as a challenge. It’s an opportunity. This is, like, deep inside us. Even me, as an excommunicated Mormon that doesn’t believe in gold plates or Joseph Smith—I still have this thing in me.

“In my play, one of the things I talk about is the Mormon smile. When we step off JetBlue [which has a Mormon CEO] from Salt Lake City at J.F.K., the smile comes on. We don’t understand why everyone’s wearing black. No one wears black in Utah!”

Most of the Mormons I spoke to were quick to reassure me that they’re not thinking about converting people all the time. (Most Mormon men go on a two-year mission, though it’s less common for women to go—in large part, because Mormon women tend to get married so young.) Strictly speaking, that may be true, but it’s also true that Mormons are constantly thinking about how they appear to the outside world; for example, they see the performing arts as a way to reach people (the benefits and pitfalls to this can be seen in the playwright and director Neil LaBute, a former Mormon, whose more recent works have taken a critical stance toward the church). “Mormons are very rooted in their faith,” Mr. Buckner told me. “They view everything as a mission.

“If they become good community members and raise a good family and set roots here, then they’re more likely to stay,” Mr. Buckner continued. “And then they can foster the understanding that we’re all part of the same human family.”

Mr. Buckner, 44, is one of those Mormons who have set roots here; he owns his own consulting business and lives on the Upper West Side with his wife and five children. “In New York City, you can get anything,” he told me one afternoon last month, in an office in the church’s large temple building near Lincoln Center. (Anyone can enter a Mormon church, but only church members who have the “recommend” can enter the more sacred parts of the temple.) A church spokesman sat with us, taking notes. “It can be difficult, but if anything, people find this a safe haven from the noise of the world,” said Mr. Buckner.

Last weekend, The New York Times Magazine explored why Americans, on the whole, have been distrustful of Mormonism, in the context of Mr. Romney’s candidacy. “Mormonism’s political problem arises, in large part, from the disconcerting split between its public and private faces. … Mormonism, it seems, is extreme in both respects: in its exaggerated normalcy and its exaggerated oddity.”

“We have a history of being secretive,” said Mary Jones, a grad student in English literature at Rutgers, who was attending Ms. Baker’s class. “Now that we’re really trying to integrate, we underestimate how interested people are.”

Nonetheless, her classmate, 29-year-old Jarom Britton, a red-haired attorney wearing a suit, said that “sometimes members get a little bit of a persecution complex. We’re guarded. We don’t want to be attacked for what we believe.”

I asked Mr. Buckner, the stake president, what he would want people to know about Mormonism. “I would want them to know I’m a follower of Christ,” he said. “I’m trying to do all I can to follow him and recognize him as my Savior.” That, of course, is relevant especially in light of continued skepticism about Mormon beliefs, especially from evangelical Christians, many of whom do not consider Mormons to be Christians.

And so the Mormons of New York have made it their mission to make the good people of Manhattan understand not only the tenets of their religion, but also that they—and their smiles—aren’t going away.

“We have a noble desire to serve our communities,” said Mr. Buckner, who also noted that historically Mormons, especially in New York, have stayed aloof from secular community affairs, choosing to remain cloistered in their church community.

But that should change, Mr. Buckner said. “We should be on school boards and such. And most of all, we need to vote.” With a community as small and yet as single-minded as theirs, it’s entirely possible that we could start seeing Mormons gradually making a bigger name for themselves in New York politics, just as they have done in Western states where Mormons are more prevalent. (Predictably, Utah has the most Mormons of any state, with nearly 1.8 million; California has 750,000, and Idaho has nearly 400,000.)

But Mormons’ rules and their emphasis on success can seem self-righteous, even smug. “It’s a little Pollyannaish and a little OCD, because everyone’s all striving to be better and improve themselves and do the right thing,” said 40-year-old Greg Allen, a former private-equity analyst who’s now a filmmaker and writer.

Mr. Allen, who has been a practicing Mormon his whole life, is bemused by all these Mormons-come-lately who are content to move to New York now that it’s been somewhat sanitized. “To be Mormon and decide to live in New York was a little odd at one point,” said Mr. Allen, who lives on the Upper West Side. “But then with Friends and Mad About You, all those happy New York TV shows that ruined New York by making it safe for everyone, that kind of changed the tenor of the Mormon population, I guess. It felt a little more normal to say you were going to stay and live in New York.”

And 26-year-old Katie Daines, who grew up on the Upper East Side and went to Spence and Harvard, said simply, “It’s been the balancing act of my life.” Ms. Daines, who is tall and rather birdlike, spoke to The Observer over a plate of French fries and a diet Coke at the Viand Café, on Madison Avenue and 78th Street. She used to work for Goldman Sachs, but quit last year and traveled, and since coming home has worked at the downtown boutique Opening Ceremony. “I grew up in the private-school scene. The hardest thing was, where are the people like me? I think a lot of people feel that way.”

These days, Ms. Daines said, “sometimes I like to go to church, sometimes I like to go out dancing.” Dating, however, “poses problems.”

Ms. Baker felt the same way. “When I was dating a Mormon guy for six months, I hung out with Mormons and it felt so easy,” she said. “But there were all these aspects of my New York life that he wasn’t interested in.”

Then again, dating non-Mormons isn’t easy either, Ms. Baker said. “I’m a decently attractive girl, and guys immediately go to—well, they see it click in their head: Oh, my God, I’m talking to a virgin.”