Silicon Valley is in the cultural, commercial, and financial center of North California.
San Francisco ( initials SF ) ( [ sæn_frənˈsɪskoʊ ] , Spanish for Saint Francis ; Spanish : [ san franˈsisko ] ) , officially the City and County of San Francisco , is the cultural , commercial , and financial center of Northern California . Silicon Valley . The region has expanded to include the southern half of the San Francisco Peninsula in San Mateo County , and southern portions of the East Bay in Alameda County .