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 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 suburb of San Francisco in the late 19th and early 20th centuries. The historical progression from native American tribal lands to Spanish, then Mexican ranches, thence to farms, ranches, and orchards, suburbs and eventually cities, is shared with the adjacent Contra Costa County
According to the U.S. Census Bureau, the county has a total area of 821 square miles (2,127 km²), of which, 738 square miles (1,910 km²) of it is land and 84 square miles (216 km²) of it (10.18%) is water.
The San Francisco Bay borders the county on the west. The crest of the Berkeley Hills form part of the northeastern boundary, and reach into the center of the county. A coastal plain several miles wide lines the bay, being home to Oakland and the most populated regions. Livermore Valley lies in the eastern part of the county.
The Hayward Fault, a major branch of the San Andreas Fault to the west, runs through the most populated parts of Alameda County, while the Calaveras Fault runs through the southeastern part of the county.
Major Highways in Alameda County
Interstate 80 (Eastshore Freeway)
Interstate 238
Interstate 580 (MacArthur Freeway/Arthur Breed Freeway)
Interstate 680 (Sinclair Freeway)
Interstate 880 (Nimitz Freeway/Cypress Freeway)
Interstate 980 (John B. Williams Freeway)
State Route 13 (Warren Freeway/Ashby Avenue/Tunnel Road)
State Route 24 (William Byron Rumford Freeway)
State Route 84
State Route 92 (Jackson Street)
State Route 123 (San Pablo Avenue)
State Route 238 (Mission Boulevard/Foothill Boulevard)
Towns and Cities in Alameda County
Alameda
Albany
Berkeley
Dublin
Emeryville
Fremont
Hayward
Livermore
Newark
Oakland
Piedmont
Pleasanton
San Leandro
Union City
Adjacent Counties
Santa Clara County, California - south
San Mateo County, California - west
San Francisco County, California - west
Contra Costa County, California - north
San Joaquin County, California - east
