Back when they owned a basic camper, Mike and Marina Wolfgram parked it on riverbanks, in rustic campgrounds and on the sides of highways.

That all changed when they bought their first luxury motor home -- a 45-foot coach the size of a yacht and, at $1 million, just as expensive. But driving in luxury created an unexpected problem for the couple -- parking.

So, after buying their coach and outfitting it with a state-of-the-art navigation system, a queen-sized bed, two phone lines and three TVs, the couple went on to invest in three lots at three different luxury RV resorts.

For the last five years, the fastest-growing segment of the RV industry has been the sale of luxury-end rigs -- a market that has grown 120-fold since 1991. That year, only 100 RVs costing $200,000 or more were sold. Last year, the number was more than 12,000.

The demand for luxury rigs such as the Wolfgrams' has given birth to a secondary industry -- posh RV parks outfitted with swimming pools, clubhouses, golf courses and private lagoons.

"It's the Ritz-Carlton of RV accommodations," said Ron Petty, president of Outdoor Resorts of America in Bermuda Dunes, Calif. The company operates 12 luxury motorcoach resorts in the United States, including the Pacific Shores Motorcoach Resort in Newport.

To the Wolfgrams, comfort is found first on the inside -- the opulent interior of their coach resembles a mansion on wheels. But it is also on the outside, in the gated community they share with other owners of luxury rigs.

In Newport, the Wolfgrams paid $150,000 for a lot ringed with flowering shrubs, facing the waves crashing on Oregon's coast. In Surprise, Ariz., their lot backs up to an 18-hole championship golf course, while their third property in Indio, Calif., has a private waterfall.

"You get to this age in life, and you want a certain level of comfort," said Mike Wolfgram, 62, who sold his house in Yuba City, Calif., to finance the new life he shares with his wife.

"It's the difference between a Motel 6 and the Sheraton," said Anne Carlson, 69, of Palm Desert, Calif., a former airline stewardess who parks her Marathon Coach on lots she and her husband own at the Newport resort. "It's like being at the Marriott, but getting to wake up in my own bed."

RVs have been a part of America's fabric since 1914, when the first commercial motor home was created by erecting a canvas tent on a trailer bed. But for decades the image of RV parks has been one of a seedy retreat.

"People think 'trailer trash.' They don't realize how much the technology has changed," said Linda Profaizer, president and chief executive of the National Association of RV Parks and Campgrounds in Falls Church, Va.

The modern motorcoach resort is the brainchild of the founding fathers of today's luxury rig, who realized their customers needed a destination for their mansions-on-wheels.

"We needed a place to park our toys," said Bob Lee, founder of Country Coach in Junction City, Ore., and developer of the Desert Shores Motorcoach Resort in Indio.

When the coaches began to get longer and wider, he said, finding the proper electrical hookups became a problem -- as did a space that was wide enough to fit the rig.

Bob Schoellhorn, chairman and chief executive of Marathon Coach in Coburg, Ore., is now majority owner of Outdoor Resorts of America Inc., which plans to add eight more resorts to its existing 12 within the next five years. Monaco Coach Corp., the second-largest maker of motor homes in the United States, and also based in Coburg, is building two resorts, including one in Las Vegas.

Of the 8,500 privately owned RV parks in the United States, Profaizer estimates that as many as 150 offer a resort-like experience. The most luxurious have amenities that rival those of the best hotels and admission rules that are stricter than many country clubs.

"We don't allow trailers. No fifth wheels. No pop-ups. No campers," said Mike Parks, manager of the Pacific Shores Motorcoach Resort in Newport. "And nothing less than 25 feet. We'll get out and measure it if we have to. It's opulence to the nth degree," he said.

The market for luxury resorts can only grow, said Schoellhorn at Marathon Coach, given the ages and tastes of baby boomers and the reluctance of many to travel overseas.

Overall, the $12 billion-a-year RV industry is booming. In June, even as oil prices reached a 13-year-high, wholesale RV shipments rose 17.8 percent over June 2003. Richard Curtin, director of consumer surveys at the University of Michigan at Ann Arbor, said wholesale shipments in 2004 are on track to set a quarter-century record.

For Mike and Marina Wolfgram, sipping gin on the verandah of their lot facing the Pacific Ocean at one of the most luxurious resorts in the country is the end of an evolution.

"We did campers. We did trailers. We slept in the dirt. We paid our dues," she said.

Stuart Carlson strolls outside his Marathon Coach in Newport, Ore., where he and his wife own an oceanside lot at Pacific Shores Motorcoach Resort.Stuart and Anne Carlson sit inside their luxury motor home, the fastest-growing segment of the RV market.