Alameda County is a county in the state of California in the United States. As of the 2010 census, the population was 1,510,271, making it the 7th-most populous county in the state. Its county seat is Oakland. Alameda County is included in the San Francisco Bay Area, occupying much of the East Bay region.Alameda County is included in the San Francisco–Oakland–Hayward, CA Metropolitan Statistical Area, which is also included in the San Jose-San Francisco-Oakland, CA Combined Statistical Area.HistoryThe 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 grove of poplars.....or a tree lined street" a name originally used to describe 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.The county seat at the time it was formed was located at Alvarado, now part of Union City. In 1856 it was moved to San Leandro, 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.
