Oakland is the largest city and the county seat of Alameda County, California, United States. A major West Coast port, Oakland is the largest city in the East Bay region of the San Francisco Bay Area, the third largest city overall in the Bay Area and the eighth most populated city in California. With a population of 440,646 in 2020, it serves as the Bay Area's trade center and economic engine: the Port of Oakland is the busiest port in Northern California, and the fifth busiest in the United States of America. An act to incorporate the city was passed on May 4, 1852, and incorporation was later approved on March 25, 1854. Oakland is a charter city.