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.