Irish Population in Contra Costa County, CA by City : 2025 Ranking & Insights

The Irish population in Contra Costa County, CA is recorded at 84,661 residents, based on the latest U.S. Census estimates. Each city in Contra Costa County, CA has some Irish population, but the county''s higher total suggests additional rural or non-municipal representation. The analysis below explores how Irish communities are spread across Contra Costa County, CA and comparable counties throughout California.

Top 5 cities with the largest Irish population in Contra Costa County

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  • 1
    Concord
    Irish population in Concord is 9,987
    8.04% of Concord population is Irish
  • 2
    Walnut Creek
    Irish population in Walnut Creek is 7,482
    10.72% of Walnut Creek population is Irish
  • 3
    Antioch
    Irish population in Antioch is 5,872
    5.07% of Antioch population is Irish
  • 4
    Brentwood
    Irish population in Brentwood is 5,499
    8.51% of Brentwood population is Irish
  • 5
    Martinez
    Irish population in Martinez is 4,966
    13.45% of Martinez population is Irish

Overview of Irish population in Contra Costa County

  • Population Count and Percentage: American Community Survey data shows Contra Costa County contains 84,661 Irish residents (7.3% of 1.2 million total county population), ranking the jurisdiction at the 97th percentile nationally among counties and 83rd percentile within California for Irish demographic concentrations across both absolute and proportional measures.
  • Comparison to State and National Averages: Census Bureau's ACS indicate Contra Costa County's Irish population of 7.3% exceeds California's state average of 5.8% while remaining below the national average of 9.4%, placing the county above regional demographic benchmarks while below national concentration levels.
  • Share of Total State Population: Official American Community Survey data documents Contra Costa County with 84,661 Irish residents, representing 3.7% of California's total Irish population of 2.3 million.
  • Population Density per Square Mile: U.S. Census Bureau's American Community Survey document Contra Costa County with 118.1 Irish Americans per square mile, just over eight times California's average density of 14.6 per square mile, placing the county among the most densely concentrated jurisdictions within the state.
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19 Cities in Contra Costa County Ranked by Irish Population

View Methodology
ACS data [1] confirm Irish populations in every incorporated city in the county, with the largest counts in Concord, Walnut Creek, Antioch, and Brentwood. The table below provides detailed figures, including total population, density measures, and demographic distributions, based on the current ACS data for all 19 incorporated cities included in this analysis*.
cities in Contra Costa County, CA ranked by Irish population count
Rank by Irish Population
City
Irish Population
% of Total City Population
% of Total Contra Costa County Irish Population
5 Year Rank Trend
1 Concord 9,987 8.04% 11.80%
2 Walnut Creek 7,482 10.72% 8.84%
3 Antioch 5,872 5.07% 6.94%
4 Brentwood 5,499 8.51% 6.50%
5 Martinez 4,966 13.45% 5.87%
6 Danville 4,953 11.41% 5.85%
7 San Ramon 4,386 5.12% 5.18%
8 3,753 8.47% 4.43%
9 3,657 10.65% 4.32%
10 3,561 14.09% 4.21%
11 3,554 3.08% 4.20%
12 3,199 16.43% 3.78%
13 1,998 11.90% 2.36%
14 1,830 16.69% 2.16%
15 1,760 2.32% 2.08%
16 1,704 6.61% 2.01%
17 1,098 5.83% 1.30%
18 907 3.46% 1.07%
19 337 1.06% 0.40%
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Methodology

This ranking list is based on data from the American Community Survey (ACS) 5-Year Estimates, conducted by the U.S. Census Bureau. The ACS is one of the most reliable sources for understanding population trends across different locations, and it provides estimates for various racial and ethnic groups at city, county, state and all geography levels down to the Census block group.
This list ranks city in Contra Costa County, CA by their Irish population, using the most recent ACS data available.

How the Census defines Irish population

The U.S. Census Bureau allows people to self-identify their ancestry, meaning individuals can write upto ancestries when responding to the survey. In this ranking, we include everyone who identifies as having Irish ancestry, whether alone or in combination with another ancestry.
Here are a few important things to know about how ancestry is reported:
  • Some people identify as Irish alone, while others identify as Irish along with another race (such as Irish and German).
  • We’ve used the “Irish alone or in any combination” category unless noted otherwise, which gives a broader picture of the Irish population in each area.

How We Ranked the Data

This ranking is based on the total number of people who identified as Irish alone or in combination in city. To provide additional context, we’ve also included two key percentages:
  1. % of Total City Population – This shows what percentage of the total state population identifies as Irish .
  2. % of Total Contra Costa County Irish Population – This tells us how much of the entire U.S. Irish population lives in that state.
To keep things simple, all population numbers have been rounded to the nearest whole number, and percentages are rounded to one decimal place. Because of rounding, some percentages may not add up to exactly 100%.

Things to Keep in Mind

Like all survey-based data, ACS estimates come with some limitations. Here are a few things to be aware of:
  • In places with very small Irish populations, the numbers may not be reported at all due to privacy protections or sampling variability in the survey.
  • Since the ACS is based on a sample, the numbers are estimates, not exact counts. That means they may slightly differ from other sources like the decennial U.S. Census.
  • City that don’t have any reported Irish population are not included in the ranking but are listed separately below for reference.
This ranking is meant to provide a clear, data-driven look at where Irish populations are most concentrated while keeping the numbers easy to understand.

Sources

  1. 2019-2023 5-Year Estimates.
  2. 2023.