Alameda County, California

Alameda County
Interactive map of Alameda County
Coordinates: 37°39′N 121°55′W / 37.65°N 121.91°W / 37.65; -121.91
Country United States
State California
RegionBay Area
IncorporatedMarch 25, 1853
Named afterRancho Arroyo de la Alameda (also see Alameda Creek)
County seatOakland
Largest cityOakland (population)
Fremont (area)
Government
 • TypeCouncil–CAO
 • BodyAlameda County Board of Supervisors
 • PresidentDavid Haubert
 • Vice PresidentLena Tam
 • Board of Supervisors
Supervisors
  • David Haubert
  • Elisa Márquez
  • Lena Tam
  • Nate Miley
  • Nikki Fortunato Bas
 • County Administrator's OfficeSusan S. Muranishi
Area
 • Total
821 sq mi (2,130 km2)
 • Land739 sq mi (1,910 km2)
 • Water82 sq mi (210 km2)
Highest elevation
3,843 ft (1,171 m)
Population
 (2020)
 • Total
1,682,353
 • Estimate 
(2024)
1,649,060
 • Density2,280/sq mi (879/km2)
GDP
 • Total$168.506 billion (2022)
Time zoneUTC−8 (Pacific Time Zone)
 • Summer (DST)UTC−7 (Pacific Daylight Time)
Area codes510, 341, 925
FIPS code06-001
Congressional districts10th, 12th, 14th, 17th
WebsiteACgov.org

Alameda County (/ˌæləˈmdə/ AL-ə-MEE-də) is located in the U.S. state of California. As of the 2020 census, the population was 1,682,353, making it the 7th-most populous county in the state and 21st most populous nationally. The county seat is Oakland. 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.

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.