You could also be thinking of South Park City, which is an old mining town from the gold rush era. It was abandoned and has since been converted into a museum; it is now part of Fairplay.
After living in Colorado for 36 years.. I got all except 2. I missed Loveland as i was actually naming Ski towns; just not the right one. And i missed Lakewood even though im at work in that city at the very moment smh.
3:29 to spare (Finished in 0:31)! However, I've lived in Colorado for 16 years and counting so not super impressive/bragworthy I suppose. Though I can see how some Colorado natives/residents might still miss some of the Denver suburbs or some of the "L" towns up north.
Never lived there, but I have family there and it's one of my favorite places in the world. I got all 20, but I'm also into geography and maps and have visited most of these cities, so I guess it helps.
I also find your score of 4/20 to be extremely appropriate for a Colorado quiz.