Back in the '70s, when the specter of school busing was scaring the double-knit pants off of suburbanites, Colorado passed the Poundstone Amendment, to prevent the City and County of Denver from annexing land. As a result, while other metropolitan areas swallowed suburbs (and their tax revenues), Denver suffered from stunted growth and seemed doomed to never pass the half-million mark in population. But now, with new-urbanism projects at Stapleton and Lowry and more infill in the Platte Valley and RiNo, Denver's growing again. In fact, according to the U.S. Census Bureau, it's now the fourth-fastest-growing county in the country, with a population of just over 600,000.