Well, parking in any given western state is not the ideal way to visit other states around it. These states are a lot bigger than eastern ones (yes, even bigger than NY). That said, some places in Colorado that are worth seeing (and others will add many more, I'm sure):
Pikes Peak and Garden of the Gods - Colorado Springs
Rocky Mt. Nat'l Park - Estes Park
Royal Gorge (if it's repaired after the fires) - near Pueblo
Durango-Silverton narrow gauge RR and Mesa Verde NP - Durango is a good base for these
anywhere up in the mountains (lots of areas)
That's just for starters, and just in Colorado. IMO, it will take you many months of month-long trips to see the western states. One month each ought to do it.
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2020 Toyota Tundra CrewMax 5.7L V8 w/ tow pkg, Equal-i-zer
2020 Lance 2375