It was a buyer's market for Kelly Middleton.

When a new job brought her family down from Maryland, they shopped for a reasonably priced house in Union County -- and found plenty to choose from.

"I can't believe the way they build neighborhoods down here," says Middleton, 29. "They're just popping up all over."

Last week the Middletons became the first residents of Bonterra, a subdivision rising in the red clay of Indian Trail. Eventually it will have 1,400 homes, and as many residents as Pineville.

Super-developments are sprouting like towns across the region. Mecklenburg County's Ballantyne? Think Shelby.

And then think bigger.

The area within 40 miles of Charlotte could double to 4 million people by 2030, by one economist's estimate. That's as if the entire city of Houston were plopped into the Piedmont. Metro Charlotte will be as big as metro Atlanta is today.

Growth means boom times for builders. But it clogs roads, packs schools and strains water supplies already hurt by years of drought. It pressures tax rates and makes it harder to find political consensus.

Growth is not inevitable. But economic and demographic trends suggest it's coming. How it shapes the physical landscape and everyday lives will turn on thousands of choices, big and small. Decisions by regular citizens -- where they live, how far they drive -- will be as important as any.

One choice affects others.

Union County spent $1.7 million for land for three new schools near Indian Trail, in part to serve Kelly Middleton's four boys and the 1,750 other students expected to come from Bonterra. The schools themselves will cost more than $50 million. Widening the two-lane roads around Bonterra will cost millions more.

"Nothing can be taken in isolation," says urban planning consultant Michael Gallis.

Because growth ignores municipal and county boundaries, issues often involve more than one government. Gallis argues that when it comes to metropolitan Charlotte, nobody's in charge.

Charlotte, for example, is building transit rails -- but only as far as the county line. Interstate 485 is spinning around the city and pulling new developments into its orbit both inside and outside Mecklenburg.

So what will the region look like? And who will decide?

Planners vs. developers

The current path, says Charlotte-Mecklenburg Planning Director Martin Cramton, offers "a doomsday scenario."Spread-out, auto-dependent suburbs continue to pop up in almost random fashion. Roads grow increasingly congested. Air gets so dirty you can taste it. Local and state governments have no money to fix problems as quickly as they arise.

"If (you) think the last 25 years have been something, you ought to see what the next 25 years will bring," Cramton says.

"We tend to operate on the loose theory that growth ... pays for itself. That's not true."

Here's what planners want: orderly growth with transportation options, strong city cores and jobs clustered along rail and highway corridors. They see transit lines like Charlotte's as magnets for high-density neighborhoods where people can walk to the train, commute to work and stop at a corner grocery on the way home. Their model: South End, where condos rise beside tracks before trains even run.

Achieving that won't be easy.

Many surrounding counties see residential development outpacing job growth, strapping local governments that rely on more lucrative corporate taxes to subsidize services. Few have the money to extend commuter rails from Mecklenburg.

"It's a fine line between the quality of life we all say we want and the economic realities of maintaining it," says Maurice Ewing, economic development director in Cabarrus County.

Crosland Co. CEO Todd Mansfield works out of an office across South Boulevard from a future light-rail station. Mansfield developed Birkdale Village, a dense, mixed-use mixture of shops and housing in north Mecklenburg. He says the market for a similar development across South Boulevard is years away.

"We're in the business of responding to what the marketplace calls for," he says. "We respond to what builders tell us they want and today they want lots in the suburbs. And that's what we deliver for them."

But Davidson Planning Director Warren Burgess says developers don't look hard enough for alternatives.

"We don't build good choices," he says. "I don't think they've really explored the market. There is a significant market ... for people who want to live in a true community with town-like character."

Some places create options.

The Atlanta Regional Commission is a multicounty planning agency that controls the metro area's transportation dollars. After decades of road-building, it encourages communities to use the money for projects such as bike trails and mixed-used shopping and residential centers that keep people off the roads.

"Are we going to stop growing out? No, I don't think so," says ARC director Chick Krautler. "There are still people who want houses on half-acre lots. ... What we didn't do in the past was to provide people with alternatives."

Atlanta's example

In 1999 federal officials cut off road money for metro Atlanta after the region failed to meet clean air guidelines. Then-Gov. Roy Barnes created a super transportation planning agency with broad powers, including the right to reject local land use plans that feed pollution and sprawl.

The Charlotte region faces a similar threat. It must comply with air guidelines by 2005 or face the loss of $6 billion in highway dollars. Counties throughout the region must agree on a plan to improve air quality.

Regional cooperation here has a slim track record. It was just a year ago that Charlotte-Mecklenburg planners held their first meeting with counterparts from the county's own small towns.

Cooperation requires compromise and potential loss of control. As Union County's planning director, Dick Black knows the obstacles. His county's 14 municipalities have a hard enough time agreeing among themselves on land use.

"Here we are trying to get our towns in one county on the same page," Black says. "Often times the relationships are more difficult within counties than between them."

Some communities are taking fledgling steps toward cooperation. For example, eight jurisdictions from Lincolnton to Concord are undertaking a study of N.C. 73, a road that connects them all.

Advocates of regional cooperation, including nonprofits such as Voices & Choices, say surveys have shown people are ready for it. A new Observer poll found 70 percent of the region's residents favor new rules designed to shape growth; 71 percent favored laws that would help the environment even if they slow economic growth.

"(People) are absolutely making the connections that more roads get in the way of air quality," says Dennis Rash of UNC Charlotte's transportation studies department. "The real test is: Will people start coupling their personal decisions with that awareness? And that's the real hard question."

Lessons from mistakes

Atlanta is learning from its missteps.

"One of our big mistakes was ... (not) recognizing that you really have to link land use and transportation decisions," says the ARC's Krautler.