1. The Missions of California were founded on October 17, 1771, when Father Junipero Serra began his journey up the coast of California to establish a chain of missions.

2. In 1989, Loma Prieta earthquake struck the San Francisco Bay Area on October 17, causing widespread damage and loss of life. The earthquake measured 6.9 on the Richter scale and lasted for only 15 seconds.

3. On October 17, 1959, the first section of the Hollywood Freeway opened in Los Angeles, revolutionizing transportation in the city and paving the way for a massive expansion of the freeway system in California.

4. On October 17, 1973, President Richard Nixon signed the Endangered Species Act into law, aimed at protecting species that were threatened with extinction. The law has since been credited with saving numerous species from extinction, including the bald eagle, grizzly bear, and gray wolf.

5. In 2017, California became the largest market in the world to legalize the sale of recreational marijuana on October 17th. The move was seen as a major shift in the state's drug policy, with advocates hoping it would lead to reduced crime and a boost in tax revenues.