Empire Mine State Historic Park

Empire Mine State Historic Park is a state-protected mine and park in the Sierra Nevada Mountains in Grass Valley, California, USA. The Empire Mine is on the National Register of Historic Places and a federal Historic District. Since 1975 California State Parks has administered and maintained the mine as a historic site. The Empire Mine is "one of the oldest, largest, deepest, longest and richest gold mines in California." Between 1850 until its closure in 1956, the Empire Mine produced 5.8 million ounces of gold, extracted from 367 miles (591 km) of underground passages. In 1850 George D. Roberts discovered gold in a quartz outcropping which became known as the Ophir Vein. As word spread that hard rock gold had been found in...