Sent this to a friend who knows his trains. He wrote back:
"Devil's Gate Viaduct on the Georgetown Loop Railroad, Georgetown, Colorado. I-70 is on the hillside in the background. A pull-off on I-70 eastbound overlooks this scene. I remember stopping there when I was a kid and my dad pointed out there used to be a railroad there. I didn't believe him. Why build a railroad way up there? Turns out it went even higher into the mountains, but didn't make it over the Divide. Served several silver mines. The line was pulled out around 1940, and rebuilt for tourist trains in the '80s. Cool place."
"Devil's Gate Viaduct on the Georgetown Loop Railroad, Georgetown, Colorado. I-70 is on the hillside in the background. A pull-off on I-70 eastbound overlooks this scene. I remember stopping there when I was a kid and my dad pointed out there used to be a railroad there. I didn't believe him. Why build a railroad way up there? Turns out it went even higher into the mountains, but didn't make it over the Divide. Served several silver mines. The line was pulled out around 1940, and rebuilt for tourist trains in the '80s. Cool place."