Oakland is the largest city and the county seat of Alameda County, California. 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 most populated city in California, and the 45th most populated city in the United States. With a population of 440,646 as of 2020, it serves as a trade center for the San Francisco Bay Area; the 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 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.