I've spent too many hours day dreaming about building a city from scratch in the middle of the country. An ideal spot would be around Wilson Lake in Kansas. It is almost equidistant from Denver, Oklahoma City (with a straight shot to Dallas) and Kansas City right in that sweet spot where high speed rail is more attractive than air travel. Bonus: there isn't an existing city there with existing governance.

I've always thought that if you are building a city from scratch, founding a University would be a great way to start. If you found it with strong programs in any or all of "architecture, ecology, economics, politics, technology, urban planning" then you get a major draw in that people studying these areas would be able to be instrumental in implementing them in a real way. When people are going to University is also one of the major pivot points in people's lives when they are willing to relocate.