California

Contra Costa

1,165,927
2020 population
1860
first census record
17
census records

About Contra Costa

Contra Costa, California, first appears in the United States federal census in 1860, when it recorded a population of 5,328. At the most recent census, in 2020, its population stood at 1,165,927.

The county's recorded population has risen across the decades to its highest level in 2020.

On the ground today, one documented military engagement has been recorded within the county, among them Mare Island / Hercules Explosion (German Sabotage 1917), and 51 places are listed on the National Register of Historic Places.

Population by decade

Census YearPopulationChart
20201,165,927
20101,049,025
2000948,816
1990803,732
1980656,380
1970558,389
1960409,030
1950298,984
1940100,450
193078,608
192053,889
191031,674
190018,046
189013,515
188012,525
18708,461
18605,328
Source

Population data from the United States decennial census, U.S. Census Bureau (public domain).

Battles & engagements in Contra Costa

Military engagements that took place in Contra Costa, California.

Mare Island / Hercules Explosion (German Sabotage 1917)
1917

Historic places in Contra Costa

National Register of Historic Places listings in Contra Costa, California.

Shadelands Ranch House
Walnut Creek
East Brother Island Light Station
Richmond
Marsh, John, House
Byron
Moraga Adobe
Orinda
Martinez City Library
Martinez
Port Chicago Naval Magazine National Memorial
Martinez
Port Costa School
Port Costa
Riverview Union High School Building
Antioch
Tucker House
Martinez
Tao House
Danville
Ford Motor Company Assembly Plant
Richmond
John Muir National Historic Site
Martinez
Eugene O'Neill National Historic Site
Danville
Hershell-Spillman Merry-Go-Round
Berkeley
Rodgers, Patrick, Farm
Pleasant Hill
Alvarado Park
Richmond
Black Diamond Mines
Antioch
Winehaven
Richmond
Rosie the Riveter-World War II Home Front National Historical Park
Richmond
New Hotel Carquinez
Richmond
Buehler, Maynard and Katharine, House
Orinda
Nystrom Elementary School-The Maritime Building
Richmond
Atchison Village Defense Housing Project, Cal. 4171-x
Richmond
Pacheco, Don Fernando, Adobe
Concord
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Everything a full report reveals about Contra Costa County, California

This page charts the census history of Contra Costa County, California. A full Aubrey report for an address here pulls together everything the historical record holds about the ground, from the earliest settlement to the twentieth century:

Overview
An interactive map of the location with historic sites, battles and Native heritage plotted, and its full story era by era.
The Land
The historic sites and place names around the location, and how this land was settled and used.
Geology
The bedrock beneath the site, its age and rock type, reaching back millions of years.
LiDAR Terrain
Laser-scanned terrain that reveals earthworks and old features hidden in the landscape.
Conflict & War
The battles, raids and skirmishes fought near here, across every era of American conflict.
The Civil War
The Civil War on this ground, 1861 to 1865: who held it, and the battles, camps and regiments nearby.
The Soldiers
The men who marched from here in the Civil War, named and traced where the record allows.
Native Heritage
The Native nations who held this land, mapped across time from before European contact to today.
Settlement
Who claimed and held this ground, from Indigenous homelands through the colonial powers to the United States.
The Community
How the town grew, who came, and what kind of place it became, traced through the census record.
Rivers & Rail
The rivers, canals and railroads that connected this place between 1830 and 1911.
Notable People
The people born, buried or genuinely tied to this exact place, with their stories.
Historical Maps
Historic maps of the location layered over how it looks today.
Finds & Access
Museum objects tied to the area, and the laws on searching, collecting and access here.
Literature
The old books, county histories and archives that mention this place, quoted with their sources.
Spotlight
A deep dive into the most remarkable, lesser-known history of the place, traced back to the record.
Points of Interest
The most significant historic sites and landmarks near the location, and why they matter.
Timeline
The whole story of the location told era by era, from first peoples to the present day.
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Frequently asked about Contra Costa

When does Contra Costa first appear in the US census?
Contra Costa, California first appears in the federal census in 1860, with a recorded population of 5,328.
What is the population of Contra Costa?
At the most recent federal census (2020), Contra Costa had a recorded population of 1,165,927.
Were any battles fought in Contra Costa?
1 documented military engagement took place in Contra Costa, including Mare Island / Hercules Explosion (German Sabotage 1917).
How many historic places are in Contra Costa?
51 sites are listed on the National Register of Historic Places in Contra Costa, California.
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