Campo Seco ("dry camp" in Spanish) is an unincorporated community in Calaveras County, California. It sits an elevation of 564 feet (172 m) above sea level and is located at 38°13′38″N 120°51′12″W. The community is in ZIP code 95226 and area code 209.
Founded by Mexicans in 1849, the mining camp was quite cosmopolitan, with forty different nationalities of miners. The town was almost destroyed by a fire in 1854, but as the placers were still producing, much of the town was rebuilt. Most of the buildings that are still standing date from after the fire. The town also contains the largest living cork oak tree in California, which was planted in 1858.
The town today is registered as California Historical Landmark #257.
The first post office was established in 1854.