The first European settlements in Nevada were the 1851 settlements at Mormon Station (now Genoa) and at the mouth of Gold Canyon (Dayton), both in the Carson River Watershed. In the 1850s and 1860s, the river was used as the route of the Carson Trail, a branch of the California Trail that allowed access to the California gold fields, as well as by the Pony Express. Gold was discovered along the river in the Silver Mountain Mining District in 1860. The 1868 Virginia and Truckee Railroad transported ore to the quartz reduction mines along the river. Virginia City, Nevada, along the lower watershed, was home to the world's greatest silver rush, the Comstock Lode in 1859. The Carson Valley provided food and forage for the silver miners and their livestock. The Comstock mining boom critically impacted the watershed and its water quality by causing deforested slopes, mine tailings, and steep raw riverbanks above channels cut into the valley floor in many places. These mining operations have also led to high levels of existing mercury concentrations within the watershed.