Settled by Mexican gold miners in 1848 and named after the Catholic parish St. Andrew, the town has been a noted mining camp since early days. The gold from the initially discovered placers gave out after a few years, but the discovery of gold in an underground river channel in 1853 revitalized the camp and it soon became a town. Mining of the channels was lucrative enough for the town to completely rebuild after fires in 1858 and 1863. The gold discovered here contributed greatly to the success of the Union during the Civil War. In 1866, San Andreas became the seat of Calaveras County. It was said to be a rendezvous location for Joaquin Murrieta. Notorious highwayman Black Bart was tried here and sent to prison.