The county's population began to grow in the mid-century as pioneers, prospectors, and entrepreneurs moved in and set up residence. During this period, settlers primarily raised cattle and farmed grain and fruit crops. Mineral mining also played a role in the economics of the county. In 1858 the great silver rush began in Napa Valley, and miners flocked to the eastern hills. While gold was being prospected in other areas of the state in the 1850s, Napa County became a center for silver and quicksilver mining. In the 1860s, mining carried on, on a large scale, with quicksilver mines operating in many areas of Napa County.