1931
- Stern Grove in the Sunset District, San Francisco opens to the public
- The Bal Tabarin nightclub opens, the same year as the 365 Club opens at 365 Market Street, San Francisco
- The state of California acquires enough land to create a small state park around the peak of Mount Diablo (pictured) in Contra Costa County
- The Radiation Laboratory is established at University of California, Berkeley by Ernest O. Lawrence