NEW YORK (CNN/Money) - As Americans have taken to the pleasures of boating, it was perhaps inevitable that many would so embrace the activity that they would abandon land altogether -- at least in their leisure time.

One sign of the times: Houseboat ownership is flourishing, with more than 20,000 in use in the United States, according to Tim Gottschalk of Houseboating World, a Web site (www.houseboatingworld.com) devoted to houseboating enthusiasts. Perhaps as many as 1,000 are produced each year.

The modern houseboat industry began on Lake Cumberland in Kentucky in the mid 1950s, according to Nancy Rimas, spokeswoman for Sumerset Houseboats, the largest and oldest of the major manufacturers.

Cumberland, the largest artificial lake east of the Mississippi, serpentines through the southern Kentucky countryside for more than a hundred miles. Its multitude of inlets and coves give it 1,200 miles of shoreline for fisherman and boaters to explore.

Gottschalk says houseboat building began there for fishermen who didn't want to leave the lake after a day of angling. Tinkerers like Jim Sharpe, founder of Sumerset, started putting cabins on boats for them.

Sharpe's first effort was a 10 by 24 foot steel-float bottom in the 1950s, says Brent Fothergill, his son-in-law who, with two of Sharpe's sons, started Sharpe Houseboats in 1997.

Fothergill says a major change in boatbuilding occurred in the 1980s when builders started to put in central heating and air.

Then, the 1990s economic boom created wealth for consumers to spend on luxurious floating palaces.

Prices now average between $150,000 and $200,000, says Gottschalk. Five or six bedrooms and three baths are not uncommon.

Sumerset builds about 90, mostly high-end, boats a year and sells them for upwards of $600,000, if not more. One comes equipped with custom wood cabinets, a granite wet bar, whirlpool tub in the master bath, and spiral staircase. Another, 117 feet long with a 20-foot beam, had a 46-foot addition put on top with a media room, wine cellar, and Irish pub.

There's a tremendous amount of customization involved. Rimas says Sumerset inventories more than 100,000 samples of fabrics, flooring, furnishings, and hardware in their design room. A boat recently sold by Sharpe included a steam shower, dumbwaiter, built-in grill, and deck cabana.

Despite the high costs, don't confuse houseboaters with yachtsmen.

"Houseboaters are not pinkie-in-the-air people," Rimas says. "Owners may have $200,000 a year in disposable income, but they still catch fish, clean fish, cook fish, and eat fish."

Fothergill says houseboats can be transported anywhere in the country, but most find homes in warm-weather states. Lakes like Cumberland don't freeze, he says, making it unnecessary to haul these dreadnaughts out for the winter.

Transporting them is not easy. Delivery routes have to be carefully planned; the boats are too tall for some roads and too wide for others. In addition, each state requires special permits and imposes its owns restrictions. It can cost well into five figures to move a big houseboat.

As investments, houseboats don't generally fare as well as more conventional real estate, according to Rimas. They require quite a bit of maintenance to keep both the structure and the engines up to speed. During the 1990s houseboats appreciated steadily in price. The past few years, however, Rimas says that NADA blue book prices of houseboats have shown they have maintained their values rather than increased them.