"When you're full-timing, it makes a big difference," says Jesse Lea, who's been camping out in La Posa LTVA for about five weeks. Since selling everything back in California six months ago, he and his wife have been on the road, living full-time in their fifth-wheel trailer. "Some people can afford to stay in overnight RV parks, but those places run $36, $45, even $80 a night. A lot of us can't afford to do that."

It's one of the cheapest rents in the country, but it doesn't get you much. In La Posa, there's about a mile of paved road leading out into the desert. Along the way are a few vault toilets, a couple places to fill up water tanks, a garbage collection area and a sewage dump. Other long-term areas might offer pay phones, but that's about it. Beyond the road and the meager services are wide-open spaces, free for the parking. And between Sept. 15 and April 15, those 11,000 open acres go from a barren landscape to a crawling metropolis, home to hundreds of thousands of RVs.

Depending on your viewpoint, these areas are either environmental and cultural travesties, or a glorious example of the American pioneer spirit (assisted by federal generosity). Certainly, in an environmental sense, LTVAs are essentially sacrifice zones, where the sparse, fragile desert ecology has been annihilated by the seasonal cities.

"You could go up on one of these hills and you could look out and see a sea of white," says Phil Corpus, pointing to the desert mounds in the distance. From where he's standing now, there's not one place around him, looking in all 360 degrees, without an RV.

Corpus has been coming out to the Quartzsite area for years, and for the past four has been the organizer of a group of RVers who rally in the LTVA every winter. They're known as the Southwest Bluebirds, a geographically dispersed group of people who drive Blue Bird Wanderlodges, a rather gargantuan brand of motorhome. Most Wanderlodges are in the 40-foot-long range, and can come equipped with 100-250-gallon fuel tanks, 100-gallon water tanks, walk-through bathrooms, cherry-wood interiors, and multiple big-screen televisions. They can cost anywhere from $50,000 to $300,000, used, which is the only way to get them these days, since the company shut down in 2009. About 70 Wanderlodges are at this rally, and they've arranged themselves into a big horseshoe. Owners mill around in the common area in the middle, while a few people prepare for the rally's barbecue later in the day. It's a vacation in the desert, and the Blue Bird owners are enjoying the organized leisure.

"It's a suburb of Quartzsite -- once a year. Come out to Blue Bird City, Ariz.," says Corpus, like the slogan of an imagined postcard.

That a huge mobile community is able to repeatedly –– and safely –– assemble in the desert like this speaks to the power of its members. Kazys Varnelis is a professor of architecture at Columbia University, and co-author of the book Blue Monday, part of which explores the city's temporary swap-meet culture. He sees the informal nature of the community outside of Quartzsite as a unique metropolitan form.

"It's curious," he says. "Sure, some cities actually function like that, but generally at some point they'll have more serious governance. But Quartzsite's never really had that. And it doesn't really seem to need it, either."

That seems to be part of the place's appeal.

"I've never seen such an interesting community," says Cindy Sunderland, who came out from California in her Blue Bird. "This is such a family."

Like an increasing number of recreational vehicle drivers, this group of people from all over North America originally met not in a campsite, but online. Corpus runs the group's Web site, which has more than 350 people on its e-mail list. Yahoo groups, discussion forums and a variety of online support clubs have added a newer, more connected level of community to an RV world formerly linked solely through formal associations like the Family Motor Coach Association and the Good Sam Club. Now, even those traditional groups have a vibrant online presence.

Deane Simpson calls them leisure nomads. He's a doctoral researcher and architecture instructor based in Copenhagen who has been doing research on America's aging RV populations. His work has looked at the concept of "unsettlement" and studied the mobile community that has formed between RVers both online and on the road.

"There are different aspects of community that are part of a more personal set of relations that have built up over a long period," says Simpson. "And then there's another community where people are really connecting online."

The desert plays host to a variety of formal and informal groups during the winter. The groups, like the Southwest Bluebirds, often organize themselves into their own neighborhoods. There's an area where gay RVers tend to camp, and another (farther away) where the nudists are. Modern-day hippies -- "rainbows," as many RVers refer to them -- stay out on other BLM-run land nearby where people can camp free for up to 14 days.