Thornton, CO, United States

With a population of just 11,353, Thornton is hardly the bustling metropolis some might expect of a Colorado city. The reality is a suburban sprawl of big box stores and cookie-cutter housing developments - hardly the Rocky Mountain idyll. Thornton's incorporation in 1956 as the first "fully planned community" in Adams County has led to a persistent bureaucratic headache, as the city juggles four separate school districts and a patchwork of transportation networks. And while the 80 miles of walking trails may be enticing, residents will have to brave the region's punishing winters. This is a city best suited for those seeking an affordable, family-friendly commuter suburb, not rugged mountain living.