The New Almaden Quicksilver Mine is located on Almaden Road, near the Casa Grande building, in the Santa Teresa Hills area of Santa Clara County. It was the oldest claimed mine in the country and was also considered the most productive mercury mine. The mine offers access to people of all abilities, so if you are concerned about challenges with movement when exploring, this is a great mine to visit. Mining began in 1845 when Mexican Cavalry Officer Captain Andres Castillero discovered the cinnabar in the painting rocks from the mine. American companies took over the mine and Captain Henry Halleck, manager of the mine, had the Casa Grande house built on the property. The mine ran on and off from the 1930's on, but eventually stopped production and closed. The mine was eventually purchased by the government and is part of the Almaden Quicksilver County Park. Today, the mine is open for visits Friday, Saturday and Sunday. The mine has undergone historic renovation, so call ahead to determine the hours and access currently permitted. The nearby mining museum is located inside of Casa Grande and includes exhibits of the shaft, equipment, offices, and a variety of artifacts from mining families in the area. The museum is a great place to learn about the history of the area and the way in which the gold rush and mining industry affected the development of the town.