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Alameda County, California
County of Alameda
Lake Merritt Oakland California panorama.jpg
CampanileMtTamalpiasSunset-original.jpg Hayward water tower, California.jpg
Lake Elizabeth in Fremont Central Park.JPG MCB-pleasanton-ca.jpg
Images, from top down, left to right: Looking southwest across Lake Merritt in Oakland, Sather Tower on the UC Berkeley campus, a water tower in Hayward, Lake Elizabeth in Fremont, Pleasanton sign
Flag of Alameda County, California
Official seal of Alameda County, California
Location in the state of California
Location in the state of California
California's location in the United States
California's location in the United States
Country  United States of America
State  California
Metropolitan area San Francisco–Oakland–Hayward
Incorporated March 25, 1853
County seat Oakland
Largest city Oakland (population and area)
 • Body Alameda County Board of Supervisors
 • Total 821 sq mi (2,130 km2)
 • Land 739 sq mi (1,910 km2)
 • Water 82 sq mi (210 km2)
Highest elevation
3,843 ft (1,171 m)
 • Total 1,510,271
 • Estimate 
 • Density 1,839.6/sq mi (710.3/km2)
Time zone UTC-8 (Pacific Time Zone)
 • Summer (DST) UTC-7 (Pacific Daylight Time)
Area codes 510, 925
FIPS code 06-001

Alameda County ( AL-ə-MEE-də) 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.


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 originally 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, 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.

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, then to farms, ranches, and orchards, then multiple city centers and suburbs, is shared with the adjacent and closely associated Contra Costa County.


The annual county fair is held at the Alameda County Fairgrounds in Pleasanton. The fair runs for three weekends from June to July. Attractions include horse racing, carnival rides, 4-H exhibits, and live bands.


View of downtown Oakland looking west across Lake Merritt.
View of Berkeley and the San Francisco Bay at nightfall.
The reconstructed mission at Mission San José (located in Fremont).

According to the U.S. Census Bureau, the county has a total area of 821 square miles (2,130 km2), of which 739 square miles (1,910 km2) is land and 82 square miles (210 km2) (10%) is water.

The San Francisco Bay borders the county on the west, and the City and County of San Francisco, California has a small land border with the city of Alameda due to land filling. 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; and is Oakland's most populous region. 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.

National protected area


A 2014 analysis found Alameda County to be the 4th most racially diverse county in the United States and the most diverse county in California.


Places by population, race, and income


Historical population
Census Pop.
1860 8,927
1870 24,237 171.5%
1880 62,976 159.8%
1890 93,864 49.0%
1900 130,197 38.7%
1910 246,131 89.0%
1920 344,177 39.8%
1930 474,883 38.0%
1940 513,011 8.0%
1950 740,315 44.3%
1960 908,209 22.7%
1970 1,073,184 18.2%
1980 1,105,379 3.0%
1990 1,279,182 15.7%
2000 1,443,741 12.9%
2010 1,510,271 4.6%
Est. 2015 1,638,215 8.5%
U.S. Decennial Census
1790–1960 1900–1990
1990–2000 2010–2015

The 2010 United States Census reported that Alameda County had a population of 1,510,271. The population density was 2,047.6 people per square mile (790.6/km²). The racial makeup of Alameda County was 649,122 (43.0%) White, 190,451 (12.6%) African American, 9,799 (0.6%) Native American, 394,560 (26.1%) Asian (9.7% Chinese, 5.5% Filipino, 4.8% Indian, 2.0% Vietnamese, 1.2% Korean, 0.8% Japanese, 2.2% Other Asian), 12,802 (0.8%) Pacific Islander, 162,540 (10.8%) from other races, and 90,997 (6.0%) from two or more races. Hispanic or Latino of any race were 339,889 persons (22.5%): 16.4% Mexican, 0.8% Puerto Rican, 0.2% Cuban, 5.1% Other Hispanic.


As of the census of 2000, there were 1,443,741 people, 523,366 households, out of which 32.6% had children under the age of 18 living within them, 47.0% married couples living together, 13.0% had a female householder with no husband present, and 35.2% were non-families. 26.0% of all households were made up of individuals and 7.3% had someone living alone who was 65 years of age or older. The average household size was 2.71 and the average family size was 3.31.

In the county, the population was spread out with 24.6% under the age of 18, 9.6% from 18 to 24, 33.9% from 25 to 44, 21.7% from 45 to 64, and 10.2% who were 65 years of age or older. The median age was 34 years. For every 100 females there were 96.60 males. For every 100 females age 18 and over, there were 94.00 males.

The median income for a household in the county was $55,946, and the median income for a family was $65,857 (these figures had risen to $66,430 and $81,341 respectively as of a 2007 estimate). Males had a median income of $47,425 versus $36,921 for females. The per capita income for the county was $26,680. About 7.7% of families and 11.0% of the population were below the poverty line, including 13.5% of those under age 18 and 8.1% of those age 65 or over.

In 2000, the largest denominational group was the Catholics (with 306,437 adherents) . The largest religious bodies were The Catholic Church (with 306,437 members) and Judaism (with 32,500 members).


The Alameda County Arts Commission, a division of the county administration, under the California Arts Council, was created in 1965. Its fifteen appointed members act in an advisory capacity to the board of supervisors, in promoting the arts. The Oakland Museum of California has a substantial collection of California art works and historical artifacts.

Parks and recreation

There are more than 350 parks located within the county. The East Bay Regional Park District operates within Alameda and neighboring Contra Costa County, with numerous parks within the county, including, Tilden Regional Park, Redwood Regional Park, Anthony Chabot Regional Park, Coyote Hills Regional Park, Ardenwood Historic Farm, and Pleasanton Ridge Regional Park. Eastshore State Park is located partially along the bay shore of northern Alameda County. The San Francisco Bay Trail, a project of the Association of Bay Area Governments, will run along the bay shore of the county. The Hayward Area Recreation and Park District is the largest special park district in California.


Major highways

  • I-80 (CA).svg Interstate 80 (Eastshore Freeway)
  • I-205 (CA).svg Interstate 205
  • I-238 (CA).svg Interstate 238
  • I-580 (CA).svg Interstate 580 (MacArthur Freeway/Arthur Breed Freeway)
  • I-680 (CA).svg Interstate 680 (Sinclair Freeway)
  • I-880 (CA).svg Interstate 880 (Nimitz Freeway/Cypress Freeway)
  • I-980 (CA).svg Interstate 980 (John B. Williams Freeway)
  • California 13.svg State Route 13 (Warren Freeway/Tunnel Road/Ashby Avenue)
  • California 24.svg State Route 24 (William Byron Rumford Freeway)
  • California 61.svg State Route 61
  • California 84.svg State Route 84
  • California 92.svg State Route 92 (Jackson Street/San Mateo Bridge)
  • California 123.svg State Route 123 (San Pablo Avenue) – formerly US 40 (CA).svg U.S. Route 40
  • California 185.svg State Route 185 (Mission Boulevard/East 14th Street)
  • California 238.svg State Route 238 (Mission Boulevard/Foothill Boulevard)
  • California 262.svg State Route 262 (Mission Boulevard)

Mass transit

  • ACE train – commuter rail using existing railroad tracks; primarily brings commuters from San Joaquin County to Santa Clara County
  • AC Transit – local bus system in western Alameda County and west Contra Costa County, with additional service across the three bridges from Alameda County to downtown San Francisco, San Mateo, and Palo Alto
  • BART – commuter rail centered on northwest Oakland, primarily serving commuters to downtown San Francisco and downtown Oakland
  • Capitol Corridor – commuter rail using existing railroad tracks, extending from San Jose to Sacramento, running through western Alameda County
  • WHEELS – bus system in the cities of southeastern Alameda County
  • Union City Transit – local city bus service within Union City in addition to AC Transit
  • Emery-Go-Round – free bus service in Emeryville.
  • Alameda / Oakland Ferry and Harbor Bay Ferry – connect Oakland, Alameda, and Bay Farm Island with downtown San Francisco
  • San Joaquin – Amtrak route between Oakland and Bakersfield through Fresno and the Central Valley
  • VTA – commuter service between southern Alameda county and job centers in the Silicon Valley
  • Dumbarton Express – additional service across the Dumbarton Bridge between Fremont and Palo Alto


The main airport is the Oakland International Airport, with two general aviation airports, the Hayward Executive Airport and Livermore Municipal Airport.


The county operates hospitals and primary care clinics, through the Alameda County Medical Center. The Alameda County Community Food Bank nonprofit provides food bank resources to residents. The Family Emergency Shelter Coalition coordinates services for homeless families.


Alameda County has eight National Historic Landmarks: The Abbey, Joaquin Miller House, First Church of Christ, Scientist, USS Hornet (CVS-12) (aircraft carrier), Lake Merritt Wild Duck Refuge, Lightship WAL-605, Relief, Paramount Theatre, Potomac (Presidential yacht), and Room 307, Gilman Hall, University of California. The county has a large number of National Historic Places, as well as a number of California Historical Landmarks.

Sister county

Alameda has a sister county: Taoyuan County, Taiwan (now Taoyuan City).



Census-designated places

Unincorporated communities

Former townships

Map of Alameda County 1878 LARGE
Map of Alameda County, 1878 (Six Townships)
  • Oakland Township – the northern portion subsequently became the cities of Berkeley and Albany.
  • Alameda Township – now essentially coterminous with the City of Alameda.
  • Brooklyn Township – mostly contained within Oakland and Piedmont.
  • Eden Township – partly incorporated into San Leandro and Hayward, the rest contains the communities of Castro Valley, San Lorenzo, and other unincorporated areas.
  • Washington Township – contains Union City, Newark, Fremont, and small unincorporated areas nearby.
  • Murray Township – Contains cities of Dublin, Pleasanton, and Livermore, and substantial unincorporated areas including Sunol.

Population ranking

The population ranking of the following table is based on the 2010 census of Alameda County.

county seat

Rank City/Town/etc. Municipal type Population (2010 Census)
1 Oakland City 390,724
2 Fremont City 214,089
3 Hayward City 144,186
4 Berkeley City 112,580
5 San Leandro City 84,950
6 Livermore City 80,968
7 Alameda City 73,812
8 Pleasanton City 70,285
9 Union City City 69,516
10 Castro Valley CDP 61,388
11 Dublin City 46,036
12 Newark City 42,573
13 San Lorenzo CDP 23,452
14 Ashland CDP 21,925
15 Albany City 18,539
16 Cherryland CDP 14,728
17 Piedmont City 10,667
18 Emeryville City 10,080
19 Fairview CDP 10,003
20 Sunol CDP 913

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