As others have stated, the best single source of information is Crosson's book "The Switzerland Trail of America." This has been re-printed several times, including paperback, so it's usually fairly easy to find on eBay, ABEbooks.com or used bookstores. I'm including a brief write-up that I must have done for some event, and a photo in Sunset of one passenger train (#30 pulling all four of the C&NW's Pullman coaches - no.s 6, 7, 8 and 9) taken from another train (probably the rear platform of one of the Barney & Smith coaches).
A BRIEF HISTORY OF THE SWITZERLAND TRAIL OF AMERICA
A complete history of the narrow gauge railroads that operated west from Boulder can be found in Forrest Crossen's The Switzerland Trail of America or "History of the Denver, Boulder & Western Railroad Co." by M. C. Poor, printed in the Railway and Locomotive Historical Society's Bulletin no. 65. Other sources include Boulder in Perspective and Boulder, Then and Now by J.B. Schooland (which cover Boulder and Colorado history) and Prospecting Our Past by Harrison Cobb (which covers mining and milling in Boulder County. This is just a refresher for those who have read these sources, or an introduction for anyone who has not.
The first railroad built to serve the mining communities of western Boulder County was the Greeley, Salt Lake and Pacific. This was a subsidiary of the Union Pacific, and shared the GSL&P name with an unrelated standard gauge UP subsidiary. The GSL&P was built up Boulder Canyon, turning up Four Mile Canyon, and terminated near Pennsylvania Gulch at the site that later became the town of Sunset. Construction of this line ran from July of 1881 through September 1883. The GSL&P, along with many other UP subsidiaries, was merged into the Union Pacific Denver and Gulf in 1890. A flood in Four Mile Canyon in 1894 wiped out most of the ex-GSL&P. The UPD&G did not rebuild the line. The GSL&P never owned any equipment All locomotives and rolling stock were borrowed from other UP subsidiaries, most from the Colorado Central.
Construction began on a new line in 1897. By January 15, 1898 the Colorado and Northwestern Railway was operating to Sunset. The route was essentially the same as the GSL&P, but the C&N was able to greatly reduce the number of times the track crossed four mile creek. Not satisfied with serving the communities along four mile creek, the C&N extended its line to Ward, completing the extension on July 1, 1898.
The railroad, which was dubbed the "Switzerland Trail of America" went into receivership in 1904, emerging under new management as the Colorado and Northwestern Railroad. Shortly after the reorganization, construction started on a branch from Sunset to Eldora.
The C&N went into receivership again in 1907. It emerged in 1909 as the Denver Boulder and Western Railroad. Business was light, with the mines slowing production, and many passengers choosing the Stanley Steamer busses over the railroad
When the Eastern Colorado Power Company began construction of Barker Dam near Nederland, two spurs were constructed across the mouth of four mile creek to unload materials to be hauled up Boulder Canyon for the pipeline, and the dam builder built a long spur from Sulphide to the Dam site. Sulfide was the site of the wye where Eldora trains were turned. After the dam was complete, business dropped off until World War 1 created a demand for tungsten, which was plentiful in the area. The surge in business was short lived, as the marked price declined when other areas began to develop tungsten mines.
After many attempts, the DB&W received permission from the Public Utilities Commission to abandon. The effective date was September 15, 1919. A flood washed out much of the line on July 3rd, and since the abandonment date was so close, the line was only repaired sufficiently to move all equipment to Boulder, and to allow scrapping. The Colorado Supreme Court reversed the PUC ruling in 1921, ordering the line to be placed back into service, but as it was essentially scrapped, the line was never reopened.
