The narrow gauge rail line, constructed between 1880 and 1882, connected the rich silver mines of the Silverton mining district with the smelters in Durango. The line formed an important transportation link for moving ores to processing centers and supplying the high mountain community with the necessities and comforts of life. From an engineering perspective, the route represents the accomplishments of late 19th century railroad builders who constructed a slender rocky ledge for the railbed through the deep and narrow Animas River canyon. The railroad continues to operate as a summer tourist attraction.

Quoted from the History Colorado website.