Copperopolis is a 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 other mining towns in the 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 big discovery of copper ore in the region (the first was nearby Telegraph City).
William K Reed & 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.
The town grew rapidly, as the need for copper during the Civil War to make bullets was great. The copper was sent to Stockton and then on to San Francisco, where it was loaded onto ships and taken around Cape Horn before finally arriving in smelters on the East Coast.
After the war ended, the expense of mining and shipping copper proved to be too high and the population dwindled as the mines closed. However, a Boston company purchased the mines in the 1880s and mining operations resumed. The town went through boom periods during the two World Wars, when demand for copper went up again. By the time the mines closed in 1946, according to the U.S. Bureau of Mines, they had produced 72,598,883 pounds of copper worth over $12 million. No copper mining has been done since.
The first post office was established in 1861.
Copperopolis has four buildings listed on the National Register of Historic Places: