1917
- The San Francisco Sausage Company is established by Italian immigrants Peter Domenici and Enrico Parducci
- Neptune Beach opens in Alameda with private picnic areas, barbecue pits, a clubhouse for dancing, and vacation cottages
- El Cerrito in Contra Costa County is incorporated
- During World War I, a major explosion of barges loaded with munitions at Mare Island Naval Shipyard killes 6 people, wounds another 31, and destroys some port facilities.