Denver & Rio Grande Western workers posing with a steam locomotive at the entrance to Toltec tunnel near the Colorado-New Mexico border. The photograph captures the extremely difficult construction challenges of building a railroad through the Rocky Mountains. Many railroad companies opted for narrow gauge, which was smaller than standard gauge and therefore offered cheaper and faster construction, at the expense of capacity. In 1883, the Denver & Rio Grande Railway completed a 772-mile narrow route through the Rocky Mountains between Denver, Colorado and Salt Lake City, Utah. The narrow gauge route was later supplanted by a standard gauge line that carried all through traffic, but enough local business remained that some sections of the narrow gauge operated through most of the 20th century. Today, steam locomotives still pull passenger trains of the Cumbres & Toltec Scenic Railroad through Toltec Tunnel. This photo appears on p. 267 of More Classic Trains by Arthur Dubin (Kalmbach, 1974).