Alameda County, California

Alameda County
Alameda County
County
	Mission Peak in the Diablo Range Oakland Livermore Valley Alameda Island Berkeley Alameda County coast on San Francisco Bay
	Flag Seal
	Interactive map of Alameda County
	Coordinates: 37°39′N 121°55′W / 37.65°N 121.91°W
Country	United States
State	California
Region	Bay Area
Incorporated	March 25, 1853
Named for	Rancho Arroyo de la Alameda (also see Alameda Creek)
County seat	Oakland
Largest city	Oakland (population); Fremont (area)
Government
• Type	Council–CAO
• Body	Alameda County Board of Supervisors
• President	David Haubert
• Vice President	Lena Tam
• Board of Supervisors	Supervisors David Haubert; Elisa Márquez; Lena Tam; Nate Miley; Nikki Fortunato Bas;
• County Administrator's Office	Susan S. Muranishi
Area
• Total	821 sq mi (2,130 km2)
• Land	739 sq mi (1,910 km2)
• Water	82 sq mi (210 km2) 10%
Highest elevation	3,843 ft (1,171 m)
Population (2020)
• Total	1,682,353
• Estimate (2025)	1,636,630
• Density	2,280/sq mi (879/km2)
GDP
• Total	$182.539 billion (2024)
Time zone	UTC−8 (Pacific Time Zone)
• Summer (DST)	UTC−7 (Pacific Daylight Time)
Area codes	510, 341, 925
FIPS code	06-001
Congressional districts	10th, 12th, 14th, 17th
Website	ACgov.org

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Alameda County (/ˌæləˈmiːdə/ ^ⓘ 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 poplar trees 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–Fremont, CA metropolitan statistical area and the San Jose–San Francisco–Oakland, CA combined statistical area.