With the discovery of copper ore in 1860 by Thomas McCarty and William K. Reed, the town of Copperopolis sprang into existence and soon became the largest producer of copper in the western United States. The population of Copperopolis grew to exceed 10,000 by 1863. The Union mine was the largest producing mine in the area, working three shafts and hundreds of men on the payroll.
During the nations three recent wars, the Civil War, World War I, World War II, much of the copper ore that was so vital to the implements of war was supplied by this area.
