High Quality Content by WIKIPEDIA articles! The East Bay is a region of the San Francisco Bay Area, California, United States and comprises both Alameda and Contra Costa Counties. It lies on the eastern shores of the San Francisco Bay and San Pablo Bay. The East Bay's principal cities include; Oakland, Berkeley, Richmond, Antioch, Concord, Walnut Creek, Hayward, Fremont, Livermore, and Pleasanton. San Francisco Bay's eastern shore was once known as "Contra Costa" (literally "opposite coast"), a name now used for and exclusively associated with Contra Costa County, which occupies the East Bay shoreline's northern quarter and extensive inland areas, amounting to about half of the land area, with the remainder in Alameda County..