San Francisco is a city in Northern California, located at the north end of the San Francisco Peninsula, surrounded by the Pacific Ocean and San Francisco Bay.  It has several nicknames, including "The City by the Bay", "Fog City", "San Fran", and "Frisco", as well as older ones like "The City that Knows How", "Baghdad by the Bay", and "The Paris of the West".

San Francisco is the cultural, commercial, and financial center of Northern California, encompassing an area of about 46.9 square miles.    It is has a density of about 18,187 people per square mile, making it the most densely settled large city in the state of California and the second-most densely populated major city in the United States after New York City. The city and its surrounding areas are known as the San Francisco Bay Area, and are a part of the larger OMB designated as San Jose-San Francisco-Oakland combined statistical area, the fifth most populous in the nation with an estimated population of 8.6 million.

San Francisco (Spanish for Saint Francis) was founded on June 29, 1776, when colonists from Spain established Presidio of San Francisco at the Golden Gate and Mission San Francisco de Asís named for St. Francis of Assisi a few miles away.  The California Gold Rush of 1849 brought rapid growth, making it the largest city on the West Coast at the time.  After three-quarters of the city was destroyed by the 1906 earthquake and fire, San Francisco was quickly rebuilt, hosting the Panama-Pacific International Exposition nine years later. In World War II, San Francisco was the port of embarkation for service members shipping out to the Pacific Theater. After the war, the confluence of returning servicemen, massive immigration, liberalizing attitudes, along with the rise of the "hippie" counterculture, the Sexual Revolution, the Peace Movement growing from opposition to United States involvement in the Vietnam War, and other factors led to the Summer of Love and the gay rights movement, cementing San Francisco as a center of liberal activism in the United States. Politically, the city votes strongly along liberal Democratic Party lines.

San Francisco is the world’s capital for high-tech, biotechnology and medical research industries as is also a principal banking and finance center.  San Francisco is also a popular tourist destination, known for its cool summers, fog, steep rolling hills, eclectic mix of architecture, and landmarks including the Golden Gate Bridge, cable cars, the former Alcatraz Federal Penitentiary, and its Chinatown district.  The international character that San Francisco has enjoyed since its founding is continued today with large numbers of immigrants from Asia, Latin America, and other parts of the world.  The city has a minority-majority population, as non-Hispanic whites comprise less than half of the population.

Primary Source: https://en.wikipedia.org/wiki/San_Francisco