1. October 18, 1866: The first Chinese theater in California, the Mandarin Theater, opened in San Francisco. It was a popular venue for Chinese opera and other cultural events, and helped to establish the city's Chinatown as a bustling cultural hub.

2. October 18, 1902: The first electric tramway in California began operation in Los Angeles. The line ran from downtown to the port of San Pedro, and was hailed as a major technological achievement that would transform transportation in the city.

3. October 18, 1937: California Governor Frank Merriam signed the state's first workers' compensation law, which provided compensation for workers injured on the job. The law was a major step forward in improving workplace safety and protecting workers' rights.

4. October 18, 1968: The new Main Library building opened in San Francisco's Civic Center. Designed by the celebrated architect Paul Rudolph, the building's futuristic design and innovative use of materials made it a landmark of modern architecture.

5. October 18, 1989: The Loma Prieta earthquake struck the San Francisco Bay Area, causing widespread damage and loss of life. The magnitude 6.9 quake caused the collapse of the Cypress Street Viaduct in Oakland and other major infrastructure damage throughout the region.