Some pretty cool pictures. The O&W was fully switched over to diesels by 1948. I can't recall all the dates at the moment, but I think I remember reading that most of the Camelbacks were retired somewhat early on (maybe soon after WW2?), with the Mountains and some Consolidations lasting in service until the end. Considering what looks like new construction still happening in the first picture, and the 1911 date on the bridge, I would hazard a guess that these pictures are from the early 1900's. Also, during the 30's, the O&W started to move away from using the railroad's initials to using the interlocking O and W emblem on their steam engines.
-Brian.