1. The first European discovery of the San Francisco Bay occurred on May 13, 1769, when Spanish explorer Gaspar de Portolá and his party spotted the bay from a nearby hill.

2. On May 13, 1850, California became the 31st state in the United States after being admitted to the Union. The state capital was also officially moved from San Jose to Sacramento on the same day.

3. The California Gold Rush, which began in 1848, was in full swing on May 13, 1850, with thousands of people flooding into the state in search of riches.

4. In 1960, the first successful human heart transplant was performed in California by Dr. Norman Shumway and his team at Stanford University. The procedure took place on May 13 and the patient, a 47-year-old man, lived for 18 days after the surgery.

5. May 13, 2015, marked the first ever statewide water restrictions in California due to a severe drought that had plagued the state for several years. Governor Jerry Brown ordered that urban water usage be cut by 25%, with violations resulting in fines of up to $500 per day.