From the plaque:
San Andreas, Heart of the Southern Mines
Settled by Mexicans in 1848. Named after Catholic parish of St. Andrew. First newspaper was published here
Sept 24, 1856. Destroyed by fire June 4, 1858,
and in 1863. County seat of Calaveras
County since 1866. Rendezvous of Joaquin
Murieta. Black Bart, notorious stage robber, tried
here and sent to prison from here. Noted mining camp since early days. Gold from
the surrounding ancient river channels and placer mines
contributed greatly to the success of the Union during
the Civil War.
Erected by Calaveras County Chamber of Commerce. October 26, 1930.