The description on the back of this postcard says “Santa Fe streamliner ascending Raton Pass, New Mexico.” At more than 7,600 feet, Raton Pass was the highest point on the Santa Fe Railroad. Since the pass is almost exactly on the border between Colorado and New Mexico, this train must be eastbound.
A highway and bridge appears in the background. What is now called the Old Raton Pass Road was not this close to the railroad, so I suspect the road in the postcard is a newer road that has since been replaced by Interstate 25. Below is another postcard I found on line that shows a heavyweight Santa Fe train descending Raton Pass about to pass under the same highway bridge that is in the background of the above postcard.