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

The Irish population in Sonoma County, CA is recorded at 59,164 residents, based on the latest U.S. Census estimates. Each city in Sonoma 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 Sonoma County, CA and comparable counties throughout California.

Top 5 cities with the largest Irish population in Sonoma County

  • 1
    Santa Rosa
    Irish population in Santa Rosa is 17,894
    10.10% of Santa Rosa population is Irish
  • 2
    Petaluma
    Irish population in Petaluma is 8,951
    15.09% of Petaluma population is Irish
  • 3
    Rohnert Park
    Irish population in Rohnert Park is 4,990
    11.22% of Rohnert Park population is Irish
  • 4
    Windsor
    Irish population in Windsor is 2,855
    10.91% of Windsor population is Irish
  • 5
    Sonoma
    Irish population in Sonoma is 2,401
    22.38% of Sonoma population is Irish

Overview of Irish population in Sonoma County

  • Population Count and Percentage: American Community Survey data document Sonoma County with 59,164 Irish residents (12.2% of 485,642 total county population), placing the jurisdiction at the 96th percentile nationally among counties and 78th percentile within California for Irish population density, with demographic concentrations among the highest nationwide.
  • Comparison to State and National Averages: Census Bureau's ACS show Sonoma County's Irish population of 12.2% surpassing both California's state average of 5.8% and the national average of 9.4%, positioning the county as a high-concentration jurisdiction exceeding demographic benchmarks across all geographic scales.
  • Share of Total State Population: Official American Community Survey data documents Sonoma County with 59,164 Irish residents, representing 2.6% of California's total Irish population of 2.3 million.
  • Population Density per Square Mile: U.S. Census Bureau's American Community Survey indicate Sonoma County's density of 37.6 Irish Americans per square mile exceeds California's average of 14.6 per square mile by two and a half times, establishing the county as a significant concentration center for Irish demographic communities.
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9 Cities in Sonoma County Ranked by Irish Population

ACS data [1] confirm Irish populations in every incorporated city in the county, with the largest counts in Santa Rosa, Petaluma, Rohnert Park, and Windsor. The table below provides detailed figures, including total population, density measures, and demographic distributions, based on the current ACS data for all 9 incorporated cities included in this analysis*.
cities in Sonoma County, CA ranked by Irish population count
Rank by Irish Population
City
Irish Population
% of Total City Population
% of Total Sonoma County Irish Population
5 Year Rank Trend
1 Santa Rosa 17,894 10.10% 30.24%
2 Petaluma 8,951 15.09% 15.13%
3 Rohnert Park 4,990 11.22% 8.43%
4 Windsor 2,855 10.91% 4.83%
5 Sonoma 2,401 22.38% 4.06%
6 Cotati 1,719 22.82% 2.91%
7 Healdsburg 1,712 15.19% 2.89%
8 1,120 15.00% 1.89%
9 846 9.47% 1.43%
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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 Sonoma 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 Sonoma 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.