 With a population of 433,031 , 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 of America.An act to incorporate the city was passed on May 4, 1852, and incorporation was later approved on March 25, 1854, which officially made Oakland a city.Oakland is a charter city.