Copperopolis is an unincorporated town and census-designated place (CDP) in Calaveras County, California, United States. The population was 3,671 at the 2010 census, up from 2,363 at the 2000 census. The town is located along State Route 4 and is registered as California Historical Landmark #296.
Unlike most of the mining towns in the Calaveras County, Copperopolis' claim to fame is not gold, but copper. It was founded in 1860 by William K. Reed, Dr. Allen Blatchly, and Thomas McCarty, at the site of the second major discovery of copper ore in the region (the first was nearby Telegraph City).
William K. Reed and Thomas McCarty founded the Union Copper Mine (and later the Keystone & Empire mines). In 1862, Reed sold out his interest in the mines and built a toll road from Copperopolis through Telegraph City. It connected with a road running westerly into Stockton. This road was called "Reeds Turnpike" and remained a toll road until 1865. Copperopolis was on the main stage road from Sonora to Sacramento.