If you are refering to the Cajon Pass Station it was out along 138 several miles East of 15 at the true Cajon Pass that the tracks all run through. There was a post office there too. A good resource for this would be the Mojave River Valley museum in Barstow. It's just north of the 15 on Barstow Road across from the big Chevron Station. Lots of good loacl history and a nice little book dept. Because Barstow is a rail hub, they have soom good early RR info.