1. The 1989 Loma Prieta earthquake: On October 27, 1989, a magnitude 6.9 earthquake struck the San Francisco Bay Area. The quake, known as the Loma Prieta earthquake, caused widespread damage and loss of life, particularly in the city of Santa Cruz and nearby areas. It remains one of the most significant earthquakes in California history.

2. The founding of San Francisco: On October 27, 1775, a Spanish exploring party led by Juan Bautista de Anza arrived at the site of present-day San Francisco, and founded a small settlement there. The city would later grow to become a major center of commerce, culture, and innovation in California and the United States.

3. The establishment of the UC system: On October 27, 1868, the University of California was established as a public research university system for the state of California. Today, the UC system comprises ten campuses across the state, including UC Berkeley, UCLA, and UC San Diego, and is widely regarded as one of the top university systems in the world.

4. The Golden Gate Bridge: On October 27, 1937, the Golden Gate Bridge officially opened to traffic, connecting the city of San Francisco with Marin County across the Golden Gate strait. The bridge, which took over four years to build at a cost of $35 million, is now one of the most iconic landmarks in California.

5. The birth of Lee Harvey Oswald: On October 27, 1939, Lee Harvey Oswald, who would later become known as the assassin of President John F. Kennedy, was born in New Orleans, Louisiana. Oswald briefly lived in California during his childhood, and later returned to the state after being discharged from the Marines in 1959.