Original 27 Counties
On February 18, 1850, California’s first Governor, Peter Burnett, signed into law the creation of the state’s original counties. They were as follows:
| Butte | Calaveras | Colusa |
| Contra Costa | El Dorado | Los Angeles |
| Marin | Mariposa | Mendocino |
| Monterey | Napa | Sacramento |
| San Diego | San Francisco | San Joaquin |
| San Luis Obispo | Santa Barbara | Santa Clara |
| Santa Cruz | Shasta | Solano |
| Sonoma | Sutter | Trinity |
| Tuolumne | Yolo | Yuba |
