Alameda County /

Alameda County is a county in the U.S. state of California. It occupies most of the East Bay region of the San Francisco Bay Area. As of the 2010 census it had a population of 1,510,271, making it the 7th largest county in the state. The county includes the cities of Oakland and Berkeley, and Oakland is its seat. The county was formed on March 25, 1853 from a large portion of Contra Costa County and a smaller portion of Santa Clara County. The Spanish word alameda means "a place where poplar trees grow", a name which originally was given to the Arroyo de la Alameda (Poplar Grove Creek). The willow and sycamore trees along the banks of the river reminded the early explorers of a road lined with trees, also known as an alameda. The county seat at the time it was formed was located at Alvarado; it was moved to San Leandro in 1856 where the county courthouse was destroyed by the devastating 1868 quake on the Hayward Fault. The county seat was then re-established in the town of Brooklyn from 1872-1875. Brooklyn is now part of Oakland, which has been the county seat since 1873. Much of what is now considered an intensively urban region, with major cities, was developed as a trolley car