Alameda County, California

Alameda County
County of Alameda
Lake Merritt Oakland California panorama.jpg
Hayward water tower, California.jpg
Lake Elizabeth in Fremont Central Park.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
Official seal of Alameda County
Interactive map of Alameda County
Location in the state of California
Location in the state of California
Country United States
State California
Region San Francisco Bay Area
Incorporated March 25, 1853[1]
Named for Rancho Arroyo de la Alameda (also see Alameda Creek)
County seat Oakland
Largest city Oakland
 • 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 1,682,353
 • Density 2,000/sq mi (790/km2)
Time zone UTC-8 (Pacific Time Zone)
 • Summer (DST) UTC-7 (Pacific Daylight Time)
Area codes 510, 341, 925
FIPS code 06-001

Alameda County (/ˌæləˈmdə/ AL-ə-MEE-də) is located in the state of California in the United States. As of the 2020 census, the population was 1,682,353,[3] making it the 7th-most populous county in the state[4] and 21st most populous nationally. The county seat is Oakland.[5] Alameda County is in the San Francisco Bay Area, occupying much of the East Bay region.

The Spanish word alameda means either "a grove of poplars...or a tree lined street." The name was originally used to describe the Arroyo de la Alameda. The willow and sycamore trees along the banks of the river reminded the early Spanish explorers of a road lined with trees.[6][7] Although a strict translation to English might be "Poplar Grove Creek," the name of the principal stream that flows through the county is now simply "Alameda Creek."

Alameda County is part of the San Francisco–Oakland–Berkeley, CA Metropolitan Statistical Area, and the San Jose–San Francisco–Oakland, CA Combined Statistical Area.


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 county seat at the time of the county's formation 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 to 1875. Brooklyn is now part of Oakland, which has been the county seat since 1873.

Much of what is now an intensively urban region was initially 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 to 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 four weekends from June to July. Attractions include horse racing, carnival rides, 4-H exhibits, and live bands.

Geography and climate

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.[8] 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; and is Oakland's most populous region. Livermore Valley lies in the eastern part of the county. Amador Valley abuts the western edge of Livermore Valley and continues west to the Pleasanton Ridge.

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.

The area near the Bay itself have a maritime Mediterranean climate whereas behind the mountains, summers are a lot warmer. The climate charts below are for Oakland and inland Livermore.

Neighboring counties

The City and County of San Francisco, California, borders the county on the west, and has a small land border with the city of Alameda, California due to land filling.[13]

Santa Clara County borders the county on the south.

San Joaquin County borders the county on the east.

Contra Costa County borders the county on the north.

Stanislaus County borders the county on the easternmost end of its southern boundary for 250 feet (76 m).


National protected area


A 2014 analysis by The Atlantic found Alameda County to be the fourth most racially diverse county in the United States—behind Aleutians West Census Area and Aleutians East Borough in Alaska, and Queens County in New York—as well as the most diverse county in California.[15]



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%
2020 1,682,353 11.4%
U.S. Decennial Census[23]
1790–1960[24] 1900–1990[25]
1990–2000[26] 2010–2019[27]

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.[28]


As of the census[30] 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[31]). 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) .[32] The largest religious bodies were the Catholic Church (with 306,437 members) and Judaism (with 32,500 members).[32]

2019 United States Census Bureau American Community Survey estimates

According to 2019 US Census Bureau estimates, Alameda County's population was 38.8% White (30.4% Non-Hispanic White and 8.4% Hispanic White), 10.7% Black or African American, 31.1% Asian, 11.5% Some Other Race, 0.8% Native American and Alaskan Native, 0.8% Pacific Islander and 6.4% from two or more races.[33]

The White population continues to remain the largest racial category in Alameda County and includes the 37.7% of Hispanics who self-identify as White. The remainder of Hispanics self-identify as Other Race (49.2%), Multiracial (8.7%), American Indian and Alaskan Native (1.9%), Black (1.5%), Asian (0.9%), and Hawaiian and Pacific Islander (0.2%).[33]

The Black population continues to decline and at 10.7% (including Black Hispanics)[33] is below the national average of 12.8% (including Black Hispanics).[34] The Black population peaked in the 1980 Census at 18.4%.[35] Alameda county has the 2nd highest percentage of Black residents in California after Solano County at 13.4%.

If Hispanics are treated as a separate category from race, Alameda County's population was 30.4% White, 30.9% Asian, 22.3% Hispanic-Latino, 10.3% Black or African American, 0.5% Some Other Race, 0.3% Native American and Alaskan Native, 0.8% Pacific Islander and 4.4% from two or more races.[36]

Asian Americans are now the largest racial/ethnic group at 30.9% (excluding Asian Hispanics).[33]

White Non-Hispanic Americans are the largest minority group at 30.4% of the population.[33]

By ethnicity, 22.3% of the total population is Hispanic-Latino (of any race) and 77.7% is Non-Hispanic (of any race). If treated as a category separate from race, Hispanics are the third largest minority group in Alameda County.[33]

The largest ancestry group of Hispanics in Alameda County (2018) are of Mexican descent (72.9% of Hispanics) followed by Salvadoran descent (5.5% of Hispanics), Guatemalan descent (3.9%), Puerto Rican descent (3.4%), Spaniard descent (2.0%), Nicaraguan descent (1.7%), Peruvian descent (1.4%), Cuban descent (1.2%), Colombian descent (1.1%), and those of other Hispanic ethnicity or of mixed Hispanic ethnicity (6.9%).[37]

Law, government and politics


The Government of Alameda County is defined and authorized under the California Constitution, California law, and the Charter of the County of Alameda.[38] Much of the Government of California is in practice the responsibility of county governments such as the Government of Alameda County, while municipalities such as the city of Oakland and the city of Berkeley provide additional, often non-essential services. The County government provides countywide services such as elections and voter registration, law enforcement, jails, vital records, property records, tax collection, and public health. In addition it is the local government for all unincorporated areas, and provides services such as law enforcement to some incorporated cities under a contract arrangement.

It is composed of the elected five-member Alameda County Board of Supervisors (BOS) as the county legislature, several other elected offices and officers including the Sheriff, the District Attorney, Assessor, Auditor-Controller/County Clerk/Recorder, Treasurer/Tax Collector, and numerous county departments and entities under the supervision of the County Administrator. In addition, several entities of the government of California have jurisdiction conterminous with Alameda County, such as the Alameda County Superior Court.

The current supervisors are:[39]

  • Scott Haggerty, district 1,
  • Richard Valle, district 2,
  • Wilma Chan, district 3,
  • Nate Miley, district 4, and
  • Keith Carson, district 5.

The Board elects a president who presides at all meetings of the Board and appoints committees to handle work involving the major programs of the county. If the president is absent for a meeting, the vice president shall be responsible. A Board election occurs every two years for these positions. Supervisor Miley is serving currently as president; Supervisor Carson is vice president.

The county's law enforcement is overseen by an elected Sheriff/Coroner and an elected District Attorney. The Sheriff supervises the deputies of the Alameda County Sheriff's Office, whose primary responsibilities include policing unincorporated areas of the county and cities within the county which contract with the Sheriff's Office for police services; providing security and law enforcement for county buildings including courthouses, the county jail and other county properties; providing support resources, such as a forensics laboratory and search and rescue capabilities, to other law enforcement agencies throughout the county; and serving the process of the county's Superior Court system. The District Attorney's office is responsible for prosecuting all criminal violations of the laws of the state of California, the county, or its constituent municipalities, in the Alameda County Superior Court. The current Sheriff is Gregory J. Ahern, who was elected in 2006, succeeding Charles Plummer, who had served in the post for 20 years. The Interim District Attorney is Nancy E. O'Malley, who was appointed to fill the position of retiring District Attorney Tom Orloff in September 2009. The Sheriff's Office operates two jails: Santa Rita Jail in Dublin, and Glenn E. Dyer Detention Facility in downtown Oakland.

The Alameda County Fire Department (ACFD)[40] was formed on July 1, 1993, as a dependent district, with the Board of Supervisors as its governing body. Municipal and specialized fire departments have been consolidated into the ACFD over the years. 1993 brought in the Castro Valley and Eden Consolidated FD, and the County Fire Patrol. San Leandro joined in 1995, Dublin in 1997, Lawrence Berkeley National Laboratory in 2002, Lawrence Livermore National Laboratory in 2007, The Alameda County Regional Emergency Communications Center in 2008, and Newark and Union City in 2010. Emeryville joined the ACFD in 2012.

The Alameda County Water District is a special district within Alameda County created to distribute water, but it is not operated by Alameda County administrators. It is operated by an elected board of directors.

Alameda County Superior Court operates in twelve separate locations throughout the county, with its central René C. Davidson Courthouse located in Oakland near Lake Merritt. Most major criminal trials and complex civil cases are heard at this location or in courtrooms within the County Administration Building across the street.

State and federal representation

In the California State Assembly, Alameda County is split between five districts:

In the California State Senate, the county is split between three districts:

In the United States House of Representatives, the county is split between three districts:


Since 1932, Alameda County has been a stronghold of the Democratic Party, with Dwight Eisenhower being the only Republican presidential nominee to have carried the county since. Prior to 1932, the county had been a Republican stronghold. Piedmont resident William F. Knowland was the Republican U.S. Senate Leader from 1953 to 1959. Even when Ronald Reagan won the national popular vote by an 18.3% margin in 1984, Walter Mondale won Alameda County by a larger margin. In 2004 it voted for John Kerry, who won over 75% of the vote. Every city and town voted Democratic.[44] George W Bush in 2004 was the last Republican to break 20% of the county's vote, his father (George H.W. Bush) in 1988 was the last to break 30% of the vote, and Ronald Reagan in 1984 was the last to break 40% of the vote (carrying 40.01%).[45]

United States presidential election results for Alameda County, California[45]
Year Republican Democratic Third party
No.  % No.  % No.  %
2020 136,309 17.61% 617,659 79.81% 19,991 2.58%
2016 95,922 14.54% 514,842 78.06% 48,779 7.40%
2012 108,182 18.12% 469,684 78.69% 19,027 3.19%
2008 119,555 19.19% 489,106 78.52% 14,252 2.29%
2004 130,911 23.29% 422,585 75.18% 8,594 1.53%
2000 119,279 24.13% 342,889 69.36% 32,168 6.51%
1996 106,581 23.07% 303,903 65.77% 51,560 11.16%
1992 109,292 20.62% 334,224 63.04% 86,629 16.34%
1988 162,815 33.99% 310,283 64.78% 5,899 1.23%
1984 192,408 40.01% 282,041 58.65% 6,425 1.34%
1980 158,531 37.96% 201,720 48.30% 57,366 13.74%
1976 155,280 38.09% 235,988 57.89% 16,413 4.03%
1972 201,862 42.84% 259,254 55.02% 10,079 2.14%
1968 153,285 37.63% 219,545 53.90% 34,519 8.47%
1964 142,998 33.46% 283,833 66.42% 509 0.12%
1960 183,354 45.61% 217,172 54.02% 1,474 0.37%
1956 192,911 52.40% 174,033 47.27% 1,187 0.32%
1952 201,976 52.69% 178,239 46.50% 3,079 0.80%
1948 150,588 46.57% 154,549 47.80% 18,194 5.63%
1944 122,982 41.83% 169,631 57.70% 1,374 0.47%
1940 116,961 43.56% 148,224 55.21% 3,311 1.23%
1936 82,352 35.09% 149,323 63.63% 3,011 1.28%
1932 89,303 43.68% 106,388 52.04% 8,761 4.29%
1928 118,539 65.42% 60,875 33.60% 1,780 0.98%
1924 81,454 61.48% 8,020 6.05% 43,016 32.47%
1920 73,177 69.11% 21,468 20.27% 11,244 10.62%
1916 51,417 50.34% 43,748 42.84% 6,966 6.82%
1912 0 0.00% 24,418 36.75% 42,034 63.25%
1908 21,380 64.24% 7,110 21.36% 4,793 14.40%
1904 19,065 70.32% 4,399 16.23% 3,646 13.45%
1900 14,324 64.64% 6,677 30.13% 1,158 5.23%
1896 13,429 60.43% 8,394 37.77% 400 1.80%
1892 8,792 47.60% 7,114 38.52% 2,564 13.88%
1888 8,840 57.18% 5,693 36.82% 928 6.00%
1884 7,471 60.26% 4,734 38.18% 193 1.56%
1880 5,899 59.65% 3,894 39.38% 96 0.97%

The California Secretary of State, as of February 2019, reports that there are 883,942 registered voters in Alameda County. 489,759 (55.4%) are registered Democrats, 95,587 (10.8%) are registered Republicans, 36,649 (4.1%) are registered to minor political parties, and 261,947 (29.6%) declined to answer. Every city, town, and unincorporated area in Alameda County has more registered Democrats than Republicans.[46]

On November 4, 2008, Alameda County voted 61.92% against Proposition 8, which won statewide, and which amended the California Constitution to ban same-sex marriage. The county garnered the sixth highest "no" vote, by percentage, of all California counties, and was the second largest county, by total voter turnout, to vote against it.[47]


The following table includes the number of incidents reported and the rate per 1,000 persons for each type of offense.

Cities by population and crime rates


The Alameda County Office of Education oversees seventeen K–12 school districts and one K–8 district in Alameda County. In all, there are approximately 10,000 teachers serving 225,000 students. The ACOE also services three community college districts with a total enrollment of approximately 55,000 students.

The Alameda County Library operates libraries in the cities of Albany, Dublin, Fremont, Newark and Union City and the unincorporated communities of Castro Valley and San Lorenzo. The cities of Alameda, Berkeley, Hayward, Livermore, Oakland, San Leandro, and Pleasanton have their own library systems.

Colleges and universities

Alameda County is home to the University of California, Berkeley, the flagship campus of the University of California system, and one of the largest and most prestigious research universities in the world.

Other colleges and universities located within Alameda county include:

School districts (K–12)


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.


The following sports teams play in Alameda County:

Parks and recreation

There are more than 350 parks located within the county.[51] 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, Pleasanton Ridge Regional Park and Vargas Plateau 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.[52] The Hayward Area Recreation and Park District is the largest special park district in California.


Major highways

Mass transit

  • Altamont Corridor Express (ACE) – commuter rail using existing railroad tracks; primarily brings commuters from San Joaquin County to Santa Clara County
  • Amtrak
    • California Zephyr – intercity train route running between Emeryville and Chicago.
    • Capitol Corridor – commuter rail using existing railroad tracks, extending from San Jose to Sacramento, running through western Alameda County
    • Coast Starlight – intercity train route running between Los Angeles and Seattle via Oakland and Emeryville
    • San Joaquin – Amtrak route between Oakland and Bakersfield through Fresno and the Central Valley
  • Bay Area Rapid Transit (BART) – rapid transit commuter rail centered on northwest Oakland, primarily serving commuters to downtown San Francisco and downtown Oakland
  • Valley Link – planned commuter rail running between the Tri-Valley and San Joaquin County (expected to commence in 2028)


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).[53]


Cities and census designated places of Alameda County


Census-designated places

Unincorporated communities

Former townships

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.[54]

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

See also