Oblivion Wyoming?
In "Last Stop: Oblivion" 12 February 1961 Bart Maverick is deported from a town by the sheriff, put on a stage out of town - I forget the name of the town. The end of the line for that stage is a stage station named Oblivion, where stages to Butte and to Denver leave either on different routes or different directions on the same stage route.
The most famous town of Butte was Butte, Montana, while the most famous Denver was Denver, Colorado.
So Butte, Montana would have been about 600 miles northwest of Denver, Colorado. and Oblivion should have been in Wyoming if it was anywhere near to halfway between them.