Claim: Oakland, California is the third largest city in the San Francisco Bay Area.

Oakland -LSB- ˈoʊklənd -RSB- is the largest city and the county seat of Alameda County , California , United States . A major West Coast port city , Oakland is the largest city in the East Bay region of the San Francisco Bay Area , the third largest city overall in the San Francisco Bay Area , the eighth largest city in California , and the 45th largest city in the United States , with a population of 419,267 . It serves as a trade center for the San Francisco Bay Area ; its Port of Oakland is the busiest port in the San Francisco Bay , the entirety of Northern California , and the fifth busiest in the United States . The city was incorporated in 1852 .   Oakland 's territory covers what was once a mosaic of California coastal terrace prairie , oak woodland , and north coastal scrub . Its land served as a rich resource when its hillside oak and redwood timber were logged to build San Francisco , and Oakland 's fertile flatland soils helped it become a prolific agricultural region . In the late 1860s , Oakland was selected as the western terminal of the Transcontinental Railroad . Following the 1906 San Francisco earthquake , many San Francisco citizens moved to Oakland , enlarging the city 's population , increasing its housing stock and improving its infrastructure . It continued to grow in the 20th century with its busy port , shipyards , and a thriving automobile manufacturing industry .   Oakland is known for its sustainability practices , including a top-ranking for usage of electricity from renewable resources . Oakland is also known for its history of political activism , as well as its professional sports franchises -LRB- such as the Oakland Raiders , Oakland Athletics and the Golden State Warriors -RRB- and major corporations , which include health care , dot-com companies , and manufacturers of household products . In addition , due to a steady influx of immigrants during the 20th century , along with thousands of African-American war-industry workers who relocated from the Deep South during the 1940s , Oakland is the most ethnically diverse major city in the country .