San Diego was not always known as San Diego! Surprised? Well, the first European to "discover" the beautiful land that would eventually become the City of San Diego was first "discovered" by a Spanish dude (no big surprise) by the name of Juan Rodríguez Cabrillo. Cabrillo was not looking for land to colonize for Spain, though, when he sailed into what's now known as San Diego Harbor. He was looking for a northwest passage which would link the Atlantic and the Pacific to shorten the voyage between the two vast oceans. Nevertheless, because his landing coincided with the eve of the feast day of St. Michael, the Archangel (September 28, 1542), he decided to dub the place San Miguel in honor of St. Michael. For decades after that, explorer after explorer just sailed on by, basically ignoring San Miguel.
Then, just a hair over 60 years later, another Spanish explorer who was sailing along the California coast, moored in the harbor and came ashore. He renamed the city San Diego after the patron saint of his armada's flagship, the San Diego de Alcalá. This time, the name apparently stuck since more than 400 years later, the place is still called San Diego. Still, Spain still wasn't interested in colonizing the area, so the area's native Americans were left in peace.
Roughly 167 years later, in the mid-1700s, Spain finally -- albeit reluctantly -- decided the time was right to colonize land along the California coast, including San Diego. Their decision was based on their wish to discourage Russian fur traders who were traveling down the coast, from settling on the land. Missionaries got right to work attempting to convert the local natives to Christianity, and Spain took control without having to go to war with them.
In 1867, when Alonzo Erastus Horton stepped ashore, beheld the settlement, and eventually bought up nearly a thousand acres and proceeded to turn it into a city. That city today is downtown San Diego, the prettiest city on the California Coast.
Today, there are a lot of great attractions in San Diego, including the world-renowned San Diego Zoo, several awesome beaches, museums like the San Diego Air & Space Museum, as well as the leading surfing school in all of Southern California—San Diego Surf School.