Most people believe they know all there is to know about Las Vegas - Sin City, founded by gangsters, a purely gambling-based economy, flowing with booze, feeding addictions, anything goes. After all, what happens in Vegas, stays in Vegas - right?

Oddly enough, the truth of Las Vegas is far stranger than what people believe.

Las Vegas celebrated its 100th birthday in 2005, making it one of the youngest cities in America. But people were coming to the Las Vegas Valley long before its official designation as an incorporated city.

It was, as many still see it, an oasis in the desert. Literally. An oasis with trees and a spring where wagon trains carrying supplies from Los Angeles to the Mormon capital in Salt Lake City could stop to rest and refill their water barrels in the mid- to late 19th Century. The first non-Indian settlement was a small fort built on the orders of Mormon leader Brigham Young in 1855; although abandoned two years later, it still stands today as a museum on Las Vegas Boulevard.

While Mormons always have played - and continue to have - a significant role in "Sin City" especially in the financial community, they are not alone in terms of religious influence. Las Vegas may have more ways and places to gamble than anywhere else on Earth, but it also is home to hundreds of houses of worship, representing an extremely wide range of religions.

Mining - especially silver - was the next major attraction bringing people to the area. As often was the case that was soon followed by a rail line. And that oasis of water made Las Vegas a major rail stop, where steam locomotives - and crew and passengers - could pick up water.

The railroad - then agriculture - joined mining as the linchpins of the Las Vegas economy for nearly half a century. And while all of those involved in those enterprises were known to play poker and other games of chance, the first formal gambling licenses were not issued until 1911.

But it was another new state law making divorce quick and easy that actually spurred the arrival of short-term visitors and money, most of them staying at small "dude ranches" - precursors, in a way, to today's luxury hotel/casinos along The Strip.

A precedent of sorts was set in 1931, when Las Vegas first experienced what has seemed a near invincibility to the economic downturns that have affected the rest of the nation through the decades. With the Depression well underway, the Las Vegas economy experienced a boom with the arrival of thousands of workers building the giant Hoover (aka Boulder) Dam. Those in charge, however, didn't want their workers losing all their money - and sleep - gambling, so they built the non-gambling town of Boulder City to house them.

The next boom was World War II and the construction of Nellis Air Force Base, which remains one of the largest and most important Air Force facilities in the country.

It was not until after the war that the foundation for today's gaming industry came into being - along with the short but storied career of one "Bugsy" Siegel and the Flamingo, which still stands (albeit considerably changed over the years) at the heart of The Strip. It also was then that gambling and tourism took over as the engine for Las Vegas' future growth.

And considerable growth it has been. As late as 1960, the entire population of Clark County barely exceeded 100, 000. Today, it is pushing - if not already over - 2 million, with an estimated 5000-to-6000 net new residents arriving every month.

Which brings up another, major misconception: The vast majority of tourists who come to Las Vegas never actually set foot in Las Vegas. The city itself is a relatively small part of the greater metropolitan area - and does not include The Strip, McCarran International Airport, the Las Vegas Convention Center or even the University of Nevada-Las Vegas.

McCarran is the nation's fifth busiest airport; unlike those above it on that list, however, McCarran is not a hub, where many passengers are simply changing planes and never leave the airport. To paraphrase the city's motto, those who fly into Vegas, stay in Vegas. At least, for an average of 3.4 nights.

The airport, which sits on the southeast edge of The Strip and has no room left to grow, will reach maximum capacity by decade's end. A new airport has been proposed for about 30 miles outside Vegas, to siphon off much of the international and other long-distance flights. If built, their combined maximum capacity will be about 90 million passengers a year, sometime in the 2020s - about double the current rate.

Las Vegas is the world's unchallenged king of hotels, boasting more than 140, 000 rooms by the end of 2007 and more than 175, 000 by the end of the decade. That tally includes 12 of the world's 15 largest hotels - from current Number 1 MGM/Grand to soon-to-be new champion, the Venetian/Palazzo.

The same is true for convention space, with three of the nation's largest convention centers plus hundreds of thousands of more square feet of meeting space in all those hotels. The result: More than 22, 000 conventions and trade shows every year - a number that is expected to grow dramatically as the available convention space increases by 50 percent in the next three years.

The average life of a hotel/casino is Las Vegas is about 25 years - making implosions of these huge complexes practically an annual festivity. In 2007, that "honor" is scheduled for the Stardust and possibly the Imperial Palace, although the recent change of ownership at Harrah's (which just bought the adjoining IP) could change that. Others reportedly being measured for wrecking balls include the New Frontier, Riviera, Las Vegas Hilton (next to the Convention Center) and Sahara.

With some coming down, others going up and existing hotels adding new towers all the time, anyone who hasn't been to Vegas in two or three years isn't likely to recognize it the next time they visit. That has been true for decades and almost certainly will remain true for decades to come.

At the moment, the biggest change in the skyline is the appearance of dozens of new high-rise condominiums - what some call the "Manhattanization" of Las Vegas. But all those new residents have to live somewhere - and, increasingly, they don't want that to be 30 miles out in the desert. Which is why the bulk of the high-rises are going up within a block of The Strip.

With all those new residents, it shouldn't be a surprise that Clark County - which comprises the Las Vegas metro area - is the fifth largest school district in the nation. About a dozen new schools open every year - many of them over-crowded on day one.

Las Vegas also is becoming a major medical center, not because of some 15 major medical facilities, but because of its expanding investment and growth in cutting-edge medical technology, training and development. In fact, the Nevada Development Authority predicts Las Vegas one day will be as well known as a center for high tech medicine as it is for gambling.

It already has become known as a major culinary center, with a goodly portion of visitors coming as much to enjoy dozens of world-class restaurants as to gamble. Or watch dozens of world-class shows, including five different productions by Cirque de Soleil. Or shop at some of the nation's largest - and most unusual - shopping centers. Or play golf on some 60 courses, among them many by the world's top championship designers.

Las Vegas remains - and almost certainly always will be - the world's premier destination for gambling and adult entertainment. Always changing, like a shimmering mirage in the desert, it is a place that is always new, no matter how many times you visit.