Southern Pacific 8321 is the lone helper on an eastbound manifest as it rolls down the hill in Cajon Pass, while an eastbound Santa Fe works up the hill towards Summit.

SP EMD SD40T-2 8321. An original Kodachrome slide from my collection.

In the desert drainage is a major concern, note the sometime trail, sometime swale in the foreground. The note Southern California "haze" is not too bad this day.