Coastal part is The South. Inland, you get Southwest. Then there’s the panhandle, and while I don’t know much about what the locals think of it, from the driver’s seat of a semi it’s indistinguishable from the flatter parts of Oklahoma. (Meanwhile, one of my favorite truck stops is in the hilly part of Oklahoma: the Chocktaw travel center in Stringtown.)
From the driver’s seat of a semi, Colorado feels like bits and pieces of its neighboring states smooshed together. You got Utahrado, New Mexirado, Wyomirado, and, yes, Nebraskarado, which is probably where the Midwestern Coloradans live. The only part where I really feel like I’m in a distinct state is the high mountain forests that shoot down the middle of the state.
Denver is probably where it is because it’s right at the intersection of quite a few of these biomes. I wouldn’t be surprised to learn it’s been a major trading center for about as long as humans have roamed the continent.