It all starts with the traffic. Heading south out of downtown Denver on Interstate 25, the traffic almost immediately engulfs you. About 15 miles later, as you turn west on Route 470, it may ease a bit -- but there's still congestion on both sides of the road. On your right, you see Target, Wal-Mart, and other familiar big-box names, a lineup broken by occasional motels, restaurants, auto-service shops, and apartment complexes.

On your left, a small strip of green grass lines the side of the road. Behind it, a parade of houses stretches as far as the eye can see. The houses are grouped roughly by size. Some are mansions; others are more modest. They look as if they were built from the same architectural mold: All of them look relatively new, and all are painted from the same earth-tone color palette. If you check your odometer, you'll see that this run of houses goes on for seven miles, and if you check the driver's-side mirror, you can just make out the identifying "Highlands Ranch" signs along the other side of the road.

Since 1981, 70,000 people have moved into Highlands Ranch, and about 9 more move into newly built houses there every day. It may be America's largest subdivision, depending on how you define the term. There's one in Irvine, California that may soon be larger. These ranches -- which aren't really ranches, but millennial versions of suburban subdivisions -- are evidence of a larger trend. Sometime last year, Americans crossed a milestone: Now slightly more than half of all U.S. residents live in the suburbs. The rate at which Americans are embracing this version of the suburban lifestyle means that every major American city could have its own version of Highlands Ranch within 25 years.

But Highlands Ranch is more than just a glimpse of the future of housing and development in the United States. It's also a barometer of how Americans feel about the legacy of land, built environment, and lifestyle that this generation is rapidly proliferating. It's a legacy about which Coloradans feel a great deal of uneasiness.

In 1995, there were 3,782,170 people living in Colorado -- most of them clustered along the eastern edge of the Rocky Mountains, where Denver, Boulder, and Colorado Springs now sit. During each of the past five years, however, nearly 50,000 Coloradan wanna-bes have arrived with their moving vans, looking for a place to live. Most of them have chosen to settle in urban areas east of the Rocky Mountains. As a consequence, a growing number of Coloradans now worry that just one generation (and a few more monster subdivisions) from now, their state will come to look like greater Los Angeles.

This concern is not unique to the urban parts of Colorado: Few people want their cities to look like Los Angeles, including many Angelenos. But in Denver, there's a sense that something unique is at stake. As the Denver metropolitan area has grown, that growth has threatened the very things that make the place so desirable. So the stakes have also grown, raising questions about lifestyle, growth, and sustainability.

To many Coloradans, Highlands Ranch is the epitome of the problem. To many others, living there is the best thing that has ever happened to them. Trying to figure out who's right is an exercise in futility, involving a host of value judgments. So here's a better way to look at the questions facing Denver -- and facing a generation of Americans who are battling the issues of affluence and community, success and sprawl: Is Highlands Ranch the best we can do? Are we keeping a promise to do it right? Or are we just taking our turn at blowing it?