of the commission was led by explorer Henry Custer, and they explored the northern district of the park, publishing their report in the 1860s. Custer's party crossed Whatcom Pass in 1858, and were the first whites to see Challenger Glacier and Hozomeen Mountain. Impressed with the scenic grandeur of the region, Custer stated, "must be seen, it cannot be described". In 1882, US Army Lieutenant Henry Hubbard Pierce led a government-sponsored exploration that traversed the western boundary of the southern section of the current park, in search of transportation routes and natural resources. As with the party led by McClellan in the 1850s, Pierce failed to find a suitable route for a railway, and only marginally suitable routes for roads. However, the expedition discovered gold in a quartz vein on the slopes of Eldorado Peak. Further expeditions by the military in 1883 and 1887 also determined that the mountains were virtually impenetrable. Explorers continued to seek out routes for wagon roads and railways and by the end of the 19th century, much of the park had been explored, but it was not until 1972 that the North Cascades Highway bisected the mountains. Mining, logging and dam construction 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. During the late 19th century and the first half of the 20th century, larger operations mined silver and lead in addition to gold, mostly with little