San Francisco (; Spanish for 'Saint Francis'), officially the City and County of San Francisco, is a commercial, financial, and cultural center of Northern California. The city proper is the fourth most populous in California, with 808,437 residents as of 2022, and covers a land area of 46.9 square miles (121 square kilometers), at the end of the San Francisco Peninsula, making it the second most densely populated large U.S. city after New York City and the fifth-most densely populated U.S. county, behind only four of the five New York City boroughs. Among the 91 U.S. cities proper with over 250,000 residents, San Francisco was ranked first by per capita income and sixth by aggregate income as of 2021. Colloquial nicknames for San Francisco include Frisco, San Fran, The City, and SF.
San Francisco was founded on June 29, 1776, when settlers from New Spain established the Presidio of San Francisco at the Golden Gate, and the Mission San Francisco de Asís a few miles away, both named for Francis of Assisi. The California Gold Rush of 1849 brought rapid growth, transforming an unimportant hamlet into a busy port, making it the largest city on the West Coast at the time; between 1870 and 1900, approximately one quarter of California's population resided in the city proper.