Cities are where good spots were x years ago, where x is somewhere between 300 and 100. The world is different with transportation/etc and the good spots don't look the same. See the flood of people to small mountain towns during covid. They weren't the best places before because they were hard to get to and from, but with highways, small airports, fiber internet, etc they are in many ways better than cities.
With enough investment in new roads and infrastructure we could easily build a huge city in Summit County, Colorado.
By definition, the carrying capacity of a small mountain town, is small.
Summit County is currently in drought. Where is more potable water for more residents going to come from? (That‘s a pretty big problem in most of the West as drought conditions show no sign of improvement.)
The cities are located where they are, because barring major changes transport costs going from cheapest to most expensive are navigable waterways > rail > road > air. Flying out of small airports is pretty expensive and not something that most Americans can afford to do regularly.
With enough investment in new roads and infrastructure we could easily build a huge city in Summit County, Colorado.