In November 1602, Sebastián Vizcaíno was sent to map the California coast. Arriving on his flagship San Diego, Vizcaíno surveyed the harbor and what are now Mission Bay and Point Loma and named the area for the Catholic Saint Didacus, a Spanish missionary more commonly known as San Diego de Alcalá.

San Diego is frequently referred to as the "Birthplace of California", as it was the first site visited and settled by Europeans on what is now the West Coast of the United States.

Because of its diversity of habitat and its position on the Pacific Flyway, San Diego County has recorded 492 different bird species, more than any other region in the country.

The Kumeyaay people migrated into the area around 1000 CE and erected villages scattered across the region, including the village of Kosa'aay in what is now Old Town, San Diego. Kosa'aay, which means "drying out place" in the Kumeyaay language, consisted of thirty to forty families living in pyramid-shaped housing structures and was supported by a freshwater spring from the hillsides.

Upon landing in San Diego Bay in 1542, Juan Rodríguez Cabrillo claimed the area for Spain, forming the basis for the settlement of Alta California 200 years later.

California grows more avocados than any other state in the U.S., and 60% of those avocados are grown in San Diego.

WD-40 has been ridding the world of annoying squeaks since 1953 when it was invented by San Diego's Rocket Chemical Company. To avoid disclosing its composition, the product was not patented. The original copy of the formula was moved to a secure bank vault in 2018.

The Whaley House, an 1857 Greek Revival style residence located in Old Town, San Diego, has been named "the most haunted house in America" by LIFE magazine and the Travel Channel's America's Most Haunted series. While filming for a local San Diego morning show in 1964, Regis Philbin visited the Whaley House and claimed to have a paranormal encounter with Mrs. Whaley herself. Philbin stated, "You know a lot people pooh-pooh it because they can't see it. But there was something going on in that house."

The primary border crossing between San Diego and Tijuana, the San Ysidro Port of Entry, is the busiest international land border crossing in the world outside of Asia.

Fast-food mega-chain Jack in the Box started out as a drive-thru hamburger stand on El Cajon Boulevard. The chain now has over 2,200 locations.