This image was made from the dome car while riding on the Rio Grande Zephyr. I've posted one of these images before, but added a previous shot approaching the famous tunnel. As stated before, this wonderful train ran between Denver and Salt Lake City. I was headed westward on my ride, and so this is the eastern portal.
This 6.2 mile bore, which pierces the continental divide, was built by the Denver & Salt Lake Railway between 1923 and 1927. The first train went through the tunnel in February of 1928. The Denver, Rio Grande & Western took over the line in 1931.
Prior to the building of the tunnel, the Denver, Northwestern and Pacific Railway (DN&P) crawled over the mountain using switchbacks, loops, and very steep grades (4%). David Moffat, on the board of the railway, conceived of the tunnel to eliminate all of that—but would not live to see it built.
This train would be discontinued in 1983 but a few months later Amtrak began running their train, the California Zephyr on this route and still does today.
Two images by Richard Koenig; taken August 30th 1979.