Empire Mine State Historic Park preserves one of California's greatest gold mines, where a quartz discovery on Ophir Hill in 1850 grew into a vast hard-rock operation in Grass Valley. Shaped by Cornish miners and technology that enabled ever deeper excavation, the mine became one of the state's oldest, largest, deepest, and richest, producing 5.8 million ounces of gold through 1956 from 367 miles of underground workings. The site also preserves the Bourn family's estate, industrial buildings, and gardens, revealing both the scale of gold mining and the community and way of life that developed around it before the mine's closure and later protection as a public historic site.