Foreign-born America, county by county

Methodology & caveats

Source

U.S. Census Bureau, American Community Survey (ACS) 5-year estimates, 2020–2024. County-level data from B05002, B05006, B05001, plus margins of error. Census tract data for the 10 largest cities from the same tables. National place-of-birth tabulations are at api.census.gov.

What "foreign-born" means here

Place-of-birth, not ancestry. A naturalized citizen who arrived from India in 1985 counts toward "India." Their U.S.-born children do not — ACS doesn't tabulate parental nativity at county or tract level, so second-generation Americans are not visible on this map. The everyday meaning of "Italian-American" or "Vietnamese-American" includes both generations; this map only shows the first.

Naturalized citizens, lawful permanent residents, students, work-visa holders, and undocumented residents are all combined under "foreign-born." The ACS systematically undercounts undocumented residents by an unknown but real amount, so figures for areas with large undocumented populations (parts of the border, large urban hubs) are biased downward.

The 5-year window

ACS 5-year estimates are averages across 2020-2024. Major recent shifts — the post-COVID Asian-immigration drop, the Venezuelan and Haitian asylum surge, the Ukrainian war influx, and the 2023 Title 42 expiration — are all smoothed rather than visible. To see post-2022 changes specifically, you'd need single-year ACS estimates (which require 65,000+ population) or the 2023 5-year as a comparison baseline.

Margins of error & reliability

Every ACS estimate carries a margin of error (MOE). For small countries in small counties, the MOE can exceed the estimate itself. The tooltip shows a colored dot indicating reliability based on the coefficient of variation:

• High: CV < 15% — estimate is reliable
• Moderate: CV 15–30% — use with caution
• Low: CV ≥ 30% — estimate may be unreliable

Tract-level estimates are much less reliable than county-level, especially for less common origins. We surface the same indicator at tract level; expect the dot to be red far more often.

Location quotient (LQ)

LQ measures concentration relative to the national average. An LQ of 1 means a county has the same share of foreign-born from country X as the U.S. as a whole. LQ = 5 means 5× more concentrated. LQ < 1 means under-represented. LQ is the standard demographic measure for spotting ethnic enclaves and avoids the "everywhere is just LA and NYC" problem of raw counts. The 1.0 line is marked on the legend.

Country definitions you should know

• China is split into three: mainland China (excl. Hong Kong & Taiwan), Hong Kong, and Taiwan. ACS treats them separately; we now do too.
• Korea is not split N/S in ACS. In practice nearly all foreign-born residents from "Korea" are from South Korea.
• United Kingdom aggregates England, Scotland, Wales, and Northern Ireland (with Crown Dependencies); ACS publishes sub-totals but most users want the aggregate.
• Czechoslovakia hasn't existed since 1993, but ACS still publishes it as a single category for older immigrants who reported it.

Choropleth distortion

Large rural counties visually shout louder than small urban ones. A 10,000-square-mile Nevada county with 4,000 immigrants looks bigger than Manhattan with 600,000. Keep scale in mind, especially in the Mountain West.

Ecological fallacy warning

A county at 25% foreign-born does not mean every neighborhood inside it is 25%. Use the "City zoom" mode to see tract-level variation inside the 10 largest cities. For other counties, internal variation can be substantial.

What's not here (yet)

• Tract-level data for cities outside the top 10.
• Trend over time (would require comparing multiple ACS year vintages).
• Second-generation Americans (would require PUMS-level analysis — ACS doesn't tabulate parental nativity at county or tract geography).

What's been added (recent)

• Year of arrival shown in the tooltip when hovering a county (four buckets: 2010+, 2000s, 1990s, pre-1990) or a city tract (binary recent / established split).
• Proportional symbols overlay (toggle "Overlay proportional dots") — circle area scales with raw count, correcting the choropleth's area distortion that makes large rural counties shout louder than small dense ones.

Related reading

For a deep dive on New York City specifically — countries of origin, settlement patterns, socioeconomic profiles and the legal paths of entry — see the NYC Department of City Planning's The Newest New Yorkers 2026, its first full update since 2013 (based on the 2023 ACS). It counts about 3.09 million foreign-born New Yorkers, with China now the single largest group of origin, just ahead of the Dominican Republic.

Code

Open source: github.com/joshgreenman1973/foreign-born-map