On June 12, 1859, the Comstock Silver Lode in Nevada was discovered. It was the first major silver discovery in the United States. From the article:
"One of the most important mining discoveries in American History, the Comstock Lode in Nevada was the first major silver discovery in the United States and virtually ended the California Gold Rush.
Discovered under what would become one of the most important gold camps in the West – Virginia City, on the eastern slope of Mt. Davidson, the mines would yield more than 500 million dollars of silver and gold ore during the first decades."