This is a trestle over the Van Duzen River built in 1913. In August 1972 I was hitchhiking around Northern California and ended up in Eureka, for reasons unknown. I hooked up with another guy and we thought we'd ride the Northwestern Pacific Railroad down to the Bay Area, or wherever.
Not knowing exactly where to get on the train in the first place, we just started walking down the tracks until we found a likely spot. I had only been hopping freights for a little over a year and my skills at finding a "likely place" were not completely honed yet — we ended up doing a lot of walking... on ballast... in the dark.