• The Golden Gate International Exposition (poster pictured, left) opens at newly created Treasure Island
• The Neptune Beach amusement park closes in Alameda
• Hewlett-Packard is founded in a garage (pictured) in Palo Alto
• Blue Shield of California is founded in San Francisco by the California Medical Association
• Consumers' Cooperative of Berkeley opens, having formed from the Berkeley Buyers' Club, which was associated with the End Poverty in California movement
• The Top of the Mark rooftop bar (pictured) is established at the top of the Mark Hopkins Hotel on Nob Hill in San Francisco
• Nuclear scientist Ernest Lawrence at the University of California, Berkeley wins the Nobel Prize for Physics for his invention of the cyclotron