The Keystone depot before it was converted to the tack room for the Keystone Resort Stables, just after abandonment in August, 1938.
The log structures to the right frame in your photo are original dwellings for folks who worked at the sawmill there, Swedes or Finns, I forget which.
The original DSP&P mainline was the paved road to the right of the building. The depot sat between the two legs of the wye; the tail of the wye was to the the left of the depot structure, in "Jack Straw Flats".
As I recall, one could walk the original South Park grade to the west, all the way to the Snake river trestle site. It was used as a riding trail and the horses hooves would sometimes unearth C&S relics, like spikes, etc. My then 4-year old son actually picked up a C&S freight car journal lid from the dirt in the trail. Good eye for one so young!
The wye was probably removed in the early 1900s. By 1918, the track to the depot was in place, but no longer in service.
A very compact terminal for a branch line layout. Only a single stub switch need be built!