The Niles Canyon Railway is a heritage railway that operates through Niles Canyon between Niles Junction and the western outskirts of Pleasanton over a portion of the former Southern Pacific Altamont Pass route.  Historically, it was the Central Pacific's original route between Sacramento and San Francisco Bay to complete the western end of the first transcontinental railroad.  As part of the transcontinental route it was later supplated by the current route via the big bridge at Benecia (the CalP), and eventually abandoned when trackage rights were obtained on the parallel Western Pacific line. 

These picture were taken on May 1, 2021 when the NCR ran a photo special with the "Skoocum" 2-4-4-2, a recently restored logging mallet.  The photo freight and our chase train both faced west, and from Sunol we backed to the end of track toward Pleasanton, from there we had a series of photo runbys until we reached Sunol, where we took a lunch break.  The morning was bright sun.  After lunch we ran non-stop to Niles Junction (and into the "marine layer" of clouds) and then worked our way east until we got back to Sunol about 4:30 p.m.  The pictures are more or less in that order.  The NCR did a good job of planning runbys, and as best as I could tell about everyone had a great time.