The New Almaden quicksilver mine in the Capitancillas range in Santa Clara County, California, United States, is the oldest and most productive quicksilver (i.e., mercury) mine in the U.S. The site was known to the Ohlone for its cinnabar long before a Mexican settler became aware of the ores in 1820. By the time they were identified as mercury, the mine was perfectly timed to supply the California Gold Rush. The mine ran intermittently after 1927 and eventually closed. It was purchased by the county and is now part of Almaden Quicksilver County Park.