The site of the historic Empire Mine, now a state historic park in Grass Valley, California. The Empire Mine was the richest hard-rock mine in the State of California, producing 5.8 million ounces of gold in its operating history of 106 years (1850-1956). George Roberts, the original discoverer of the gold soon sold his interest and by 1869 William Bourn Sr. owned controlling interest. The Bourn family maintained control of the mine until 1929 when it was sold to Newmont Mining. It ceased operation in 1956. In 1975 the state purchased the surface property as the Empire Mine State Historic Park. Photo by Carol Highsmith.