I am always amazed at the effort photographers have gone to to take a unique shot. This was probably one of those, as it must have taken some effort to get to the bottom of a small canyon way out in the mountains to capture this one. The engine is Sumpter Valley Ry. #50 which was a 10 wheeler built in 1916 for the railroad. #50 seems to have been used frequently on the extension from Austin MP 59 to Prairie City MP 80. There were a couple of large trestles on this line, so I suspect this in taken at one of them. Note the car behind #50 is one of the railroad's three refrigerator cars, identified by the hinged doors vs. a sliding door on a regular box car. The body of refer car #3 survives at SVRR, so who knows, this might be it. The scan is from the Martin E. Hansen Collection in the SVRR Archive.