Tourists spent a combined $15 billion last year at the Strip's various casino resorts. Sixty percent of that revenue — $9 billion — was from noncasino sources ranging from hotel rooms to restaurants, some as costly as New York's best, to high-end retailers that pay dearly for a spot inside the sprawling malls that are a staple of today's Las Vegas casino.

These revenue sources are proving enticing even to an old-line player like Boyd Gaming, a middle-market casino company that had ceded the high-end market to the likes of MGM and the Venetian. But with the announcement of its plans for the $4.4 billion Echelon Place, Boyd made clear it was going upscale, too.

"We considered a variety of options," said Robert L. Boughner, a longtime Boyd executive who is overseeing the Echelon project. "But ultimately we concluded that there were very compelling reasons to enter the premium tier."

Concerns over future limits on water supplies might ultimately slow development here. Eventually, tourists might tire of fighting the daily traffic jams that snarl the Strip and nearby freeways, or grow frustrated negotiating McCarran International Airport, which seems in a perpetual state of crisis.

But those problems have not hampered Las Vegas' success so far. The city had just under 39 million visitors in 2006, according to the Las Vegas Convention and Visitors Authority — an 86 percent increase over the 21 million visiting the city in 1990.

And in anticipation of handling even larger hordes of tourists, McCarran is in the first year of a five-year, $4 billion makeover. Meanwhile, officials are looking into adding a second airport at Ivanpah Valley, 30 miles from Las Vegas.

"People have been predicting dating back to 1955 that Las Vegas will reach a saturation point," said David G. Schwartz, author of "Roll the Bones," a history of gambling, and director of the Center for Gaming Research at the University of Nevada, Las Vegas. "But me, I wouldn't bet against casino growth."