Sonoma County, California was established on February 18, 1850 and named for a Coast Miwok and Pomo legend of Sonoma, the Valley of the Moon! Its county seat is Santa Rosa, and its fair is also held in Santa Rosa! You might recognize Fort Ross, the town of Bodega, the Petrified Forest, Mission San Francisco Solano, Jack London State Historical Park, and of course, many famous wineries, which are located in this county!