This was somewhere around Alamosa, CO. I was vacationing in the Midwest and happen to spot this from a local road, maybe half a mile away. It was on a very rarely used segment of track, possibly abandoned. This unit has since got a new lease on life running passenger excursion trains for the Saratoga & North Creek Railway in New York State.
Photographer edit: I positively identified the location as Del Norte, CO at a grade crossing for Hanna Lane upon extensive Google Maps research and retracing my route. I concluded that the place where the engine is located in this photograph is about 2 miles from the end of track. I remember miles of hoppers also being stored on this same line. A very interesting piece of railroading.