You are in the CarrTracks website Picture Gallery.
Train OMD (Overland Mail Denver) comes into Julesburg and pauses briefly on the mainline west of town.
I went to the other end of the siding to get one more picture and missed an eastbound. You can see it in the background. In 1937, UP replaced many of the semaphore signals with 101 color light signals between Julesburg and Denver. Disk 77