The New Almaden mine is the site of the first mercury deposit discovered on the American continent and has yielded metal of greater value than that of any other mine in the State, producing nearly one-third of the country's supply of mercury. The ore deposit was discovered in 1824 but not recognized as a mercury deposit until 1846. At that time, the town was renamed New Almaden after the Almaden mine in Spain, the world's greatest mercury producer. Until the discovery of the cyanide process in 1887, quicksilver was the chief reduction agent used in processing gold and silver. The metal extracted from the New Almaden mine thus made possible the rapid development of gold and silver quartz mining in California and the Comstock Lode in Nevada during the 1850s and 1860s. Since then, production has fluctuated with the opening and exhausting of ore deposits. In 1927 mining activity was terminated for the first time since 1849. Mining was resumed during World War II. The mine is inactive today. A few of the 1850s wooden and adobe structures, offices, mine structures and old furnace buildings remain. The site became a National Historic Landmark in 1964 and part of Santa Clara County's park district in 1975.