Between 2000 and 2006, Arizona's Maricopa county gained nearly 700,000 new residents, making it the fastest-growing county in the united states. Its fastest-growing town, once a faded highway pit stop, is now a 25,000-person phoenix exurb—that could swell to 400,000 over the next 25 years. Welcome to buckeye, Ariz., where ambitious planners are trying to keep the bedroom-community doldrums at bay. Please build carefully.

UNTIL RECENTLY, people in Buckeye, Ariz., thought the town's heyday was behind them. Buckeye sprang up in the late 1880s as a farming community alongside the new Buckeye Canal in what was then the Territory of Arizona. For decades, travelers crossing the Sonoran Desert saw Buckeye from Monroe Avenue, its main street, which doubled as the old U.S. Highway 80. Commissioned in 1926, 80 was the first road from coast to coast that was open all year, and it brought traffic moving right through downtown Buckeye between Phoenix, 35 miles to the east, and Southern California. But in the 1970s, Highway 80 was outmoded by Interstate 10 a few miles north, and strangers with money to spend mostly stopped coming.

Today, however, they are back in droves. Whereas Interstate 10 once threatened to suck the life out of Buckeye, it has recently proved to be one of the keys to the town's incredible reawakening—as a beeline toward more affordable housing beyond Phoenix's outer ring. Earlier this decade, developers began laying claim to huge pieces of land around Buckeye for new subdivisions and shopping centers. Across much of the Phoenix area, this influx has already brought miles of neighborhoods where houses sit rather far from shops, services, or anything fun, so it's hard to walk from here to there.

Buckeye—given the fast pace of its development—might be the last place you would expect to find anything smarter. But the town's planners and politicians are trying to get ahead of the vacuum that a developer's nature abhors, and design, of all things, a sustainable suburb. Over the past few years, they have been seriously overworked.

The town hasn't a moment to lose. Last year, Forbes magazine listed Buckeye as the second-fastest-growing suburb in the nation (after Lincoln, Calif., outside Sacramento). Between 2000 and 2005, Buckeye's population increased by nearly 200 percent, to 25,406. Three other towns nearby—Surprise, Goodyear, and Avondale—also were among the 10 fastest-growing suburbs on the Forbes list. The latter three towns, which have an air of polished newness along their palm-lined shopping strips and are filled with people speaking in Midwestern accents, butt up against the White Tank Mountains—the edge of the Valley of the Sun and long that of the Phoenix metropolitan area. But Phoenix's population pressure has begun to break around the mountains on vast tracts of desert, studded with tall saguaro cactus and brushy palo verde trees and undulating westward down to the Hassayampa River.

Over the past several years, the town of Buckeye has annexed 370 square miles of this land into its corporate limits, and its total planning area, which it intends to annex eventually, measures 598 square miles, which is larger than Phoenix. From its northernmost corporate limit to its southernmost, Buckeye runs about 45 miles long. From east to west, it is 24 miles wide.

Right now, across much of this terrain, it doesn't look as if much is going on, particularly along the Sun Valley Parkway, a four-lane divided road that stretches north from Interstate 10 into the desert before turning east back to Surprise. It has been called the Road to Nowhere. Off the interstate, a sign on the parkway cautions that there are no services for the next 35 miles.

“You're still driving through the heart of Buckeye,” said Phil Marcotte, the chief building official for the town, who was doing the actual driving. Marcotte, who started work for the town in 1994, when it had about 5,600 people, offered to show me around the vast tracts of Buckeye where developers are laying seed for 22 approved master planned communities that are expected, by 2030, to hold more than 400,000 people.

It all seems unlikely. But as you cruise a few miles up the parkway from the interstate into the scrubland, an oasis of sprinkler-fed green lawns appears on the left. It is Tartesso West, a 5,500-acre master planned community where home builders such as Hacienda, Atreus, Pulte, and Canterra are erecting the first dozens of 21,790 planned housing units around a series of neighborhood parks. They are mostly attractive, single-family stuccoish houses with multiple gables and xeriscaped front yards, sunning under high-voltage lines drawn from the Palo Verde Nuclear Generating Station off to the southwest. A sign near the entrance advertised houses starting from $199,999.

“They're giving them away!” observed Richard Rohrback, Buckeye's senior building inspector, who had joined us for the drive.

“Yeah, but we're still buildin' em,” Marcotte said.