The desire of the Mormon settlements for economic self-sufficiency led missionaries to mine lead at Potosi. In 1856 Nathaniel V. Jones was sent to recover ore from the "Mountain of Lead," 30 miles southwest of the mission at Las Vegas Springs. About 9,000 pounds were recovered before smelting difficulties forced the remote mine to be abandoned in 1857, making Potosi the first abandoned mine in Nevada. In 1861 California mining interests reopened the mine, and a smelter and rock cabins housing 100 busy miners formed the mining camp of Potosi. Even more extensive operations followed after the transcontinental Salt Lake and San Pedro R.R., now Union Pacific, was built through the county in 1905. During World War I, Potosi was an important source of zinc.