In my experience both as a railfan and a railroader the term "express" was simply a marketing term. It certainly had no meaning in terms of the rules governing train dispatching. I suspect it was a much abused term, much like many marketing descriptions. In a post WW2 market brochure for the train put out by the DRGW, the train is referred to simply as the "San Juan". But predecessors I believe had different names over the years, including the Colorado New Mexico Express, or something like that.
JBWX
Edited 1 time(s). Last edit at 01/13/2021 12:39PM by John West.