Largest Irish population, US counties · 2020
US counties ranked by the number of residents who are Irish ancestry, from the 2023 American Community Survey detailed-origin tables. Each list covers the full eligible universe; download the complete data as CSV. Cook County, Illinois leads at 448,570. 3,134 counties qualify in total. Massachusetts carries 5 of the top 25 entries.
UPDATED 2026-06-06 · DATA: US CENSUS BUREAU ACS 5-YEAR ESTIMATES
Frequently asked
Which county has the highest irish population?
Cook County, Illinois ranks #1 with 448,570 (2020 American Community Survey).
What are the top 5 counties by irish population?
Cook County, Illinois, Maricopa County, Arizona, Los Angeles County, California, Middlesex County, Massachusetts, Suffolk County, New York.
How many counties are in this ranking?
3,134 counties qualify after filtering for population minimums and data availability. The ranking covers 2020 ACS 5-year data.
How is irish population measured?
Number of residents who are Irish ancestry (Ancestry, ACS detailed tables). Source: US Census Bureau, American Community Survey 5-year estimates (2020).