Denver is the western overlap
Denver belongs to this region as the practical western gateway before the horizon opens into the plains. Chamberlin Observatory also gives the region a real astronomy stop inside the city, even though the darkest nights happen much farther east and southeast.
From Denver, one road bends northeast toward Pawnee and Jackson Lake while another heads southeast through Pueblo toward John Martin, Kim and Comanche.
The horizon gets bigger as the map gets emptier
The mountains give Colorado drama. The plains give it scale. With very little terrain blocking the view, a meteor can run a long way across the sky and the Milky Way can arc from one side of the landscape to the other.
If you want a huge sky more than a dramatic foreground, this is the branch to remember.
The local hub changes depending on which plains you chose
Denver is the western starting point, but once the trip commits to the plains the useful hub changes. Fort Morgan and the I-76 corridor make more sense for the northeast. Pueblo becomes the better handoff for the southeast, with Lamar and La Junta taking over once you are deep into the plains.
There is no reason to keep routing everything back through Denver once the trip is committed to one side.
Bring what you need
South and east of Kim, towns, traffic and lights get thin fast. That is exactly why the sky can get so good. It is also why fuel, water, a flat tire or a wrong turn matter more here than they do near a resort town.
An empty roadside is not automatically public land or a legal campsite. Know where you are parking before dark. Carry fuel and water. Download the map. Have a second plan.
Out here, self-reliance is part of the observing equipment.