Being a Utah resident presently, I was interested to learn that "St. George, in the southwestern part of Utah, was the fastest-growing metro area between 2000 and 2006, with a growth of 39.8 percent to total 126,000 on July 1, 2006." Let me explain some reasons why this has been the case. First St. George is about a 90 minute drive from Las Vegas, but Utah is a state where no gambling is allowed. I believe that there are some people who enjoy gambling but don't want to live in the go-go atmosphere of Vegas itself. For them, St. George is an ideal location.
Second, St. George is within a couple of hours drive of some of the most famous national parks and wilderness areas in the US, including Zion National Park, Grand Staircase-Escalante National Monument, and Glen Canyon National Recreation Area (which includes giant Lake Powell).
Third, St. George is about a four-hour drive from the Salt Lake City metro area which has a population of over a million people. So the city is midway between two prospering metros and has a warm winter climate similar to Las Vegas.
Interestingly, the metro with the overall largest increase in number of people during the time period in question turned out to be Atlanta, GA, which "gained 890,000 residents from April 1, 2000, to July 1, 2006." In the past it seems cities in California, Phoenix, and Dallas had been the leaders. This could be partly attributable to people leaving hurricane-prone parts of the South for a nearby city that is far enough inland to avoid hurricanes generally.