Central Oregon & Pacific uses mostly EMD GP38(-x) units for traction, 4-axle locos of the late 60s or early 70s. A reliable type with thousands of units built, sold for low prices on the used market, but only 2000 hp. Seven units are seen here on the northern approach to the Siskiyou pass.
© Larry Tuttle, used with permission. Larry provides lots of information about the Siskiyou line on his own website. There are more photos of trains crossing the Siskiyou pass at the original location of this photo.