For most of the way between Palm Springs and Phoenix, Interstate 10 cuts a straight line through the desert; a brick on the accelerator could drive it. Most people don't find too many reasons to stop, except maybe to fill the gas tank or the stomach. The landscape is relentlessly rocky and beige, except for the green valley at Blythe, where the last remnants of the Colorado River are siphoned off to irrigate alfalfa, cotton and other crops that should not grow in a place this dry and harsh.

Seventeen miles beyond Blythe and the Arizona border, towering signs for gas stations and fast food joints hint at a middle-of-nowhere stopping point, the kind of one-dimensional town that wants you to spend your money and get back on the road as quickly as possible. But as you come closer, you notice a sprawling community that should have no reason to exist beyond the standard few blocks clustered just off the interstate. Specks of white twinkle in the desert like little pockets of misplaced snow. Each one is a fiberglass rooftop belonging to one of the thousands upon thousands of recreational vehicles that briefly turn this stretch of desert into a booming urban center.

This is Quartzsite, Ariz. From the middle of December into the first few weeks of February, this small town, population 3,500, becomes the center of the RV universe. Up to a million vehicles, representing a significant chunk of the 8 million or so RVs on the road in the U.S., roll through during "the season," when swap meets and trade shows lure vendors, tourists and anyone with a home on wheels into town. Winnebagos and Bounders and Itascas flood the city and its surroundings, where an informal community blossoms every winter like a rare flower.

The invaders create an impromptu city -- a place where thousands of nomads, following the drift of seasons and the pull of highways, come together to create a community even more vibrant than the permanent habitations they left behind.

A quick scan of just one of the town's RV parks this January reveals license plates from almost every American state and Canadian province, from New York to British Columbia. They've swapped gray skies, ice, snow and freezing temperatures for the hard light of southern Arizona's winter, with average temperatures that hover around 60 to 70 degrees during the day.

But it's not just the warm weather that draws these people. Every winter, along with its other attractions -- this is the burial place of "Hi Jolly," a Syrian-born camel driver who hauled freight across the Arizona desert in the 1800s -- Quartzsite becomes the swap-meet capital of the world.

"If it's for sale in the United States, you'll find it in Quartzsite," says Richard Olson, an Arkansas native who's been coming to Quartzsite for more than 15 years. The town has about a dozen swap-meet areas that host a variety of shows and sales throughout the season, with more than 2,000 vendors, hawking everything from kitchenware to wagon wheels, in town at any given time.

Wearing a headset and a speaker tied to a fanny pack, exhibitor Beverly Malone catches the curious ears and eyes of a few people walking past her booth. She's a tiny woman, so she climbs three steps to demonstrate the ease with which her product -- a telescoping flagpole -- can raise and lower Old Glory, whether from the back of a Winnebago or the grassy front yard of whatever brick-and-mortar home these RVers ditched for the winter.

Three people are sucked into her pitch: Two of them middle-aged men in black hats that display their military affiliations during the Vietnam War. The third is an overweight woman who's resting on a walker that doubles as a chair. Like the vast majority of Quartzsite's visitors, they are white, over 50, and politically right of center. Before they commit to a sale, one of the men wants to make sure the cascading pole can carry the flag at half-staff. Malone gets that question a lot. "When President Reagan died, our phones lit up like a Christmas tree," she says.