Mineral prospectors entered the North Cascades region, and by the 1850s were doing placer mining along the banks of the Skagit River in search of gold. In the 1870s, placer mining also commenced along Ruby Creek, and hundreds of miners came to the region even though it was difficult to access. Most mining activity along Ruby Creek had ended by the 1880s, but was soon replaced by hard rock mining for silver and other minerals. This second period of mining lasted from the 1890s to the 1940s, but was only marginally more lucrative. Miners were hampered by short working seasons, difficult terrain, low quantities of ore and a lack of financial investment. Miners built some of the first trails and roads into portions of the backcountry, some of which involved intricate engineering, including bridges over the numerous streams and dynamiting rock ledges above steep gorges during trail construction. One mining company built a series of flumes, the longest of which was over , to transport lumber and to supply water for use in their hydraulic mining operation.