mine on United States Geological Survey topographic maps as the Blue Stones Mine. This tunnel exposed a "five-foot vein of ore varying in values from $16 to $25 per ton." It was concluded that the "Guinn Mountain area has little or no economic potential," despite listings of important mineral strikes in period newspapers. Further, "ten samples collected in the area contained only negligible amounts of any metal. Samples from the Avalon placer claim, located on the South Fork [of] Middle Boulder Creek north of Guinn Mountain, and from the creek bottom were collected and panned; no gold was found." Despite this record, gold claims were nevertheless worked nearby with no published record of success. Rollins Pass as an historic railroad route Early railroad endeavors There were multiple prior efforts to build a railroad over Rollins Pass in the 19th century and all attempts were met with impassable engineering challenges, financing issues, or both: GHS, Jefferson, & Boulder County Railroad and Wagon Road (A.N. Rogers' line) in 1867; U.P. in 1866; Kansas Pacific in 1869; Colorado Railroad (B. & M. subsidiary) in 1884—two tunnels located; Denver, Utah & Pacific in 1881 (construction started and tunnel located). The remains of the latter tunneling attempt can still be seen on the northern slope of the rock wall at Yankee Doodle Lake and the detritus from the attempted excavation of the tunnel was placed at the northernmost part of the lake where pulverized granite tailings can be seen rising out of the water. These tailings were definitively from the 1880s tunneling efforts as they are not visible in the early stereoscopic images from the wagon road era of Yankee Doodle Lake; further, the attempted tunnel was not part of the later rail line that ultimately summited Rollins Pass. The Moffat Road over Rollins Pass In the early 20th century, David Moffat, a Denver banker, established the Denver, Northwestern and Pacific Railway with the intention of building a railroad from Denver toward Salt Lake City, Utah by way of a tunnel under the Continental Divide. Surveys began in April 1902 and construction was started in January 1903, beginning on the east side of Rollins Pass. However, the railway only reached Craig, Colorado. This entire line from Denver to Craig was known as the Moffat Road. The line included a stretch over the top of the Continental Divide, at Rollins Pass, with a two to four