1. The first New Year's Day Tournament of Roses Parade was held in Pasadena on December 31, 1890. It featured horse-drawn carriages decorated with flowers, and it has since become an iconic annual event in California.

2. On December 31, 1915, the world's first commercial airline passenger flight took off from San Francisco's Marina District. The flight, operated by the St. Petersburg-Tampa Airboat Line, carried one passenger and lasted 23 minutes.

3. In 1949, a 7.3 magnitude earthquake struck Southern California on December 31, causing widespread damage and resulting in 12 deaths. Known as the "Inglewood earthquake," it was one of the largest earthquakes to hit the region in the 20th century.

4. On December 31, 1972, the last American combat troops left Vietnam, ending the United States' military involvement in the war. Many California soldiers were among those who served in Vietnam, and the conflict touched countless families throughout the state.

5. In 2017, a new law took effect on December 31st that legalized recreational marijuana in California. The state became the largest in the country to allow the use and sale of cannabis for adult use, a significant milestone in the ongoing evolution of California's drug laws.