Back when most of Atlantic Station existed on paper and in developers' minds — before lofts, green space and IKEA — it had a number.

30363. Five digits meant to roll off the tongue and guide mail carriers. It's Atlantic Station's very own ZIP code, a number specifically requested by developers, assigned by the U.S. Postal Service and soon to be splashed across T-shirts, Web sites, signs and any other marketable surface.

"That was very deliberate," says Brian Leary, vice president of AIG Global Real Estate Investment Corp., the Atlantic Station developer. "We've been using that ZIP code as a lifestyle statement. We want them to think 'I am 30363.'"

The way Beverly Hills is 90210, thank you Aaron Spelling.

The way Harvard is 02138, as the magazine 02138 will tell you.

The way Buckhead is 30305, as ads for million-dollar real estate tout.

Postal pride

It's been a long time since ZIP codes were just a tool to sort letters. They're how we find a place to live, how some insurance rates are set, how retailers calculate what's on our store shelves. They're a concise way to say where we live, who we are and mostly, how we fit in.

Developers built Atlantic Station to fit certain types of people — environmentally conscious singles and families who like shopping, hate commuting and still want to be, literally, in the middle of it all. That meant creating a sense of community from scratch in a place that didn't exist.

"What clearer way than to have your own ZIP code?" Leary says.

Atlantic Station developers requested a new ZIP in 2003, then massaged the numbers until they agreed on a ZIP code that was memorable, marketable and easier for sorting mail.

Much to the chagrin of the Postal Service, requests for new or different ZIP codes are often for the wrong reasons.

ZIP codes can't be changed to raise home values or shrink auto insurance bills.

The Postal Service stance is sympathetic, but firm: ZIP codes exist to deliver mail.

All the identity-crisising, keeping up with the Joneses and resale values? That's our own fault.

"Hijacked" is the word Postal Service spokesman Michael Miles uses to describe how ZIP codes are used and abused.

Everybody knows them, everybody has one and everybody can find them, which makes them the perfect tool for categorizing people.

"It's the lowest level of geography," says Steve Moore, public relations director of Claritas, a market research company. "It's what people identify with as far as a standard."

Typing a ZIP code into his company's database will turn up snippets of insight into a ZIP code's residents. The information is rarely dead-on, but familiar and detailed enough that people often ask how some company in California knows them so well.

"The answer, simply, is that you told us," Moore says.

You told them when you gave the clerk at Urban Outfitters your address, when all your friends fell for the short-lived banana coconut drink at your neighborhood Starbucks, when Nielsen recorded that you flip between Speed and Lifetime networks to relax at home.

People classify themselves by choosing to live in certain ZIP codes, or dress a certain way, or eat certain foods, Moore says. Marketers just put those classifications, along with demographic data, crime statistics and other public information, into an organized, business-friendly system.

Getting in with the in crowd

Grouping by ZIP codes isn't perfect. Some ZIPs are clear-cut, like Atlantic Station's, but many incorporate several neighborhoods with their own characteristics and values.

Ursula Henry lives in the northeast chunk of 30318 in a "wonderful" neighborhood with "great" schools and rising home values. But she happens to share a ZIP code with the Fulton County Jail and some notoriously high crime stats.

In August, she signed a letter from her neighborhood association asking to be realigned with 30327, 30309 or maybe 30325. If they had their pick, they'd go with 30305.

Henry knows the cachet of that ZIP code. As a Realtor, she stresses to clients that living in that section of Buckhead is more about lifestyle, status and investment than address.

"Atlanta very much is into perception," Henry says.

The letter to the Postal Service shared property value concerns, insurance woes, community identity issues and mail delivery annoyances.

"While we understand that ZIP codes were designed for the sole purpose of efficiency of mail delivery," the letter said, "they have taken on some additional roles that are outside your control."

The Postal Service hasn't responded.

Civic pride

Major growth can lead to large-scale ZIP code realignments, regardless of whether people want them. Atlanta's suburbs went through this 10 years ago, with a one-year grace period before envelopes needed to have the new codes.

But smaller shifts, like the one Henry requested, happen incidentally, sometimes only after serious lobbying.

Johns Creek wanted to be a city with the whole shebang: local pride, local police, local post office. The pride came easily when residents voted in 2006 to create their own government. The police department debuts this month. The post office, and the unique ZIP code that would come with it, could take years.

"The No. 1 reason is emotional," says Johns Creek Mayor Mike Bodker. "People want the pride of saying, 'This is Johns Creek, this is my city, this is my ZIP code —"

He wants to rattle off five numbers, but he can't, because they don't exist. Beyond the civic pride and

"90210 syndrome," he says, it's a matter of convenience. His post office is 35 minutes away in Alpharetta.

But the Postal Service says delivery is more efficient as it is now, with most residents writing Johns Creek as their city, but adding ZIP codes from Alpharetta, Suwanee, Roswell and Duluth.

When changes are allowed, inevitably, confusion abounds. Stationery, checks and business cards go to waste.

Marketing tool

It turns out that some people aren't aspirational ZIP code watchers; they like where they are.

Take 30307. Claritas' marketing database reveals it to be a diverse ZIP code with ranges of incomes, backgrounds and interests. It's got strong bohemian and suburban streaks. (Moore, the Claritas spokesman, was agog: "For marketers, this could be a test ZIP. If I'm selling a product that can cross over from affluent to middle, I've hit the mother lode.")

Residents already know that. When Atlantic Station was barely a construction site, residents in Little Five Points, Candler Park and Lake Claire slapped on bumper stickers that declared 30307 not just a ZIP code, but "a lifestyle."

The sticker sells at Donna Van Gogh's Artists' Market in Candler Park. Standing under a painting that says, "It takes a village," shop owner Iris Hale says that if our ZIP codes define us to outsiders, it only makes sense that we'll settle into the ZIP code that fits us best.

"There's a tribal component to the human animal, they want to group, they feel more protected," says Hale, who opened the shop 14 years ago on a block now busy with the Flying Biscuit, Full Moon Records and Dr. Bombay's coffee shop. "They want to go where like-minded people are. It's what makes humans both wonderful and awful.

"What people find is that they're not alone."

When too few people lived in Atlantic Station to call it a community, 30363 was a line on an envelope. Five years later, with buildings up and an active, engaged neighborhood growing, Leary, the developer, says they want the ZIP code to mean more.

First, they had to build a common lifestyle, Leary says, "or it's just a number."