This was a 3-foot narrow gauge line that was built from Denver, west through the Clear Creek canyon as far west as Georgetown and Silver Plume in 1883 and 1884. It was originally constructed by Union Pacific but eventually was transferred to Burlington subsidiary Colorado and Southern, and tapped mines in the area; as in other areas the mines were only profitable for a few years and freight loadings diminished over time. The line served as a scenic tourist route for several years but closed during the depression.
The segment from Silver Plume to Idaho Springs was abandoned first; the Idaho Springs to Golden was abandoned in the 1940s.
East of Golden the line was eventually standard gauged and today is still in service. The Coors Brewery (now Molson Coors) has a freight yard in the area; there is also a spur that connects to the Colorado Railroad Museum.
Much of the right-of-way between Idaho Springs and Golden was used for US Highway 6. Between Idaho Springs and Georgetown, some segments of I-70 (which was built over US 6 in part) uses the same right-of-way. Between Georgetown and Silver Plume I-70 was built on the north side of the valley; the former C&S ran on the south side. A short segment of the line, including a high trestle, was rebuilt in the 1970s and 1980s as the Georgetown Loop Railroad. The GLRR offers several daily trips over the rebuilt section during the summer tourist season.
Thanks to Mike Palmer for contributing information about this route.