Census-designated place · Virginia
Union Mill, Virginia
Union Mill, census-designated place, in Fairfax County, Virginia. Union Mill had 4,997 residents in the 2020 Census, a full count; the ACS 2020-2024 5-year estimates put it at 4,484 (±668). GEOID 5180029.
Residents, 2020 Census
4,997
Census count or controlled total
ACS 2020-2024 estimate: 4,484 ±668
Median household income
$250,000 or more
The survey's top or bottom value; no margin is published
Virginia: $93,170
Median home value
$961,400
±$50,233 (90% margin)
Virginia: $383,700
Median gross rent
$2,365
±$1,707 (90% margin)
Virginia: $1,579
Where is Union Mill and what county is it in?
Union Mill is a census-designated place: an unincorporated community the Census Bureau draws for counting, with no city government of its own, in Fairfax County, Virginia. It covers 10.0 square miles of land, 500 residents per square mile in 2020.
Union Mill is in the Washington-Arlington-Alexandria, DC-VA-MD-WV metropolitan statistical area, which takes in 23 counties (Census Bureau delineation, July 2023).
Source: 2024 Gazetteer and 2020 place-by-county files, U.S. Census Bureau · Census reference files
How many people live in Union Mill, and is it growing?
The 2020 Census counted 4,997 residents in Union Mill, a full count rather than a sample. The 2020-2024 American Community Survey, a sample, estimates 4,484 (±668).
The Census Bureau publishes yearly population estimates for incorporated places only; Union Mill is a census-designated place, so its figures come from the ACS and the 2020 Census.
| Measure | Union Mill | Fairfax County | Change since 2015-2019 |
|---|---|---|---|
| Total population | 4,484 ±668 | 1,147,837 | – |
| Households | 1,416 ±189 | 414,101 | – |
| Average household size | 3.17 ±0.25 | 2.75 | – |
| Housing units | 1,440 ±195 | 430,047 | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026); Census PEP Vintage 2025 (SUB-EST2025, CO-EST2025); 2020 Census P.L. 94-171 · Check it at data.census.gov
Who lives in Union Mill?
The median resident of Union Mill is 47.3 years old; 22.8% are under 18 and 23.5% are 65 or older. The largest group is non-Hispanic white residents at 45.0%, then non-Hispanic Asian residents at 39.0%. 30.1% of residents were born outside the United States.
| Measure | Union Mill | Fairfax County | Change since 2015-2019 |
|---|---|---|---|
| Median age | 47.3 ±3.9 | 39.1 | – |
| Under 18 years | 22.8% ±4.9 pts | 22.9% | – |
| 65 years and over | 23.5% ±4.4 pts | 15.0% | – |
| Male | 48.0% ±4.3 pts | 49.9% | – |
| Hispanic or Latino (any race) | 6.2% ±3.8 pts | 17.6% | – |
| White alone, not Hispanic | 45.0% ±7.5 pts | 46.8% | – |
| Black or African American alone, not Hispanic | 2.0% ±1.6 pts | 9.4% | – |
| Asian alone, not Hispanic | 39.0% ±8.1 pts | 19.9% | – |
| American Indian and Alaska Native alone, not Hispanic | 0.0% ±0.9 pts | 0.1% | – |
| Native Hawaiian and Other Pacific Islander alone, not Hispanic | 0.0% ±0.9 pts | 0.0% | – |
| Two or more races, not Hispanic | 6.9% ±3.8 pts | 5.4% | – |
| Some other race alone, not Hispanic | 1.0% ±1.1 pts | 0.8% | – |
| Born outside the United States | 30.1% ±4.8 pts | 30.8% | – |
| Speak a language other than English at home (age 5+) | 34.7% ±6.6 pts | 39.0% | – |
| Civilian veterans (age 18+) | 8.0% ±2.8 pts | 7.5% | – |
| With a disability | 7.1% ±2.4 pts | 8.0% | – |
| No health insurance coverage | 6.9% ±6.7 pts | 7.1% | – |
| High school graduate or higher (age 25+) | 97.4% ±2.0 pts | 93.2% | – |
| Bachelor's degree or higher (age 25+) | 71.1% ±5.8 pts | 65.0% | – |
| Graduate or professional degree (age 25+) | 33.7% ±7.3 pts | 33.0% | – |
| Lived in the same house a year earlier | 91.1% ±4.3 pts | 87.0% | – |
| Moved from another state in the past year | 0.0% ±0.9 pts | 3.2% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profiles DP02, DP05) · Check it at data.census.gov
What do households in Union Mill earn?
Half of Union Mill's 1,416 households earn less than $250,000 or more a year (), against $153,637 in Fairfax County and $93,170 in Virginia. 4.4% of residents live below the poverty line.
| Measure | Union Mill | Fairfax County | Change since 2015-2019 |
|---|---|---|---|
| Median household income | $250,000 or more | $153,637 | – |
| Mean household income | $311,043 ±$46,375 | $195,941 | – |
| Per capita income | $96,507 ±$16,164 | $71,828 | – |
| People below the poverty line | 4.4% ±2.3 pts | 5.9% | – |
| Children under 18 below the poverty line | 1.7% ±2.6 pts | 7.2% | – |
| Households receiving SNAP | 2.7% ±3.2 pts | 4.3% | – |
| Households with a computer | 100.0% ±2.8 pts | 98.4% | – |
| Households with a broadband subscription | 100.0% ±2.8 pts | 96.4% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP03) · Check it at data.census.gov
What does housing cost in Union Mill?
Owners occupy 94.8% of Union Mill's occupied homes and renters 5.2%. The median owner-occupied home is valued at $961,400 by its owner (±$50,233).
| Measure | Union Mill | Fairfax County | Change since 2015-2019 |
|---|---|---|---|
| Median home value (owner-occupied) | $961,400 ±$50,233 | $732,800 | – |
| Median gross rent | $2,365 ±$1,707 | $2,276 | – |
| Renters paying 35% or more of income on rent | 42.1% ±44.5 pts | 36.3% | – |
| Median monthly owner costs, with a mortgage | $3,842 ±$342 | $3,227 | – |
| Owner-occupied homes | 94.8% ±3.5 pts | 68.6% | – |
| Renter-occupied homes | 5.2% ±3.5 pts | 31.4% | – |
| Housing units | 1,440 ±195 | 430,047 | – |
| Homeowner vacancy rate | 0.0% ±2.9 pts | 0.4% | – |
| Rental vacancy rate | 0.0% ±38.2 pts | 4.4% | – |
| Single-family detached homes | 92.6% ±5.4 pts | 45.5% | – |
| Mobile homes | 0.0% ±2.7 pts | 0.5% | – |
| Built 2020 or later | 0.0% ±2.7 pts | 1.3% | – |
| Built 2010 to 2019 | 3.5% ±3.1 pts | 7.2% | – |
| Built 1939 or earlier | 3.5% ±2.7 pts | 1.1% | – |
| Households with no vehicle | 0.0% ±2.8 pts | 4.8% | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP04) · Check it at data.census.gov
How do people in Union Mill work and get to work?
64.0% of Union Mill's workers drive alone and 28.2% work from home. The average trip to work takes 36.6 minutes.
| Measure | Union Mill | Fairfax County | Change since 2015-2019 |
|---|---|---|---|
| In the labor force (age 16+) | 61.3% ±5.8 pts | 70.8% | – |
| Unemployment rate | 2.5% ±2.1 pts | 4.2% | – |
| Drove alone to work | 64.0% ±7.9 pts | 55.4% | – |
| Carpooled | 4.4% ±4.5 pts | 7.7% | – |
| Public transportation | 2.1% ±2.5 pts | 4.7% | – |
| Walked | 0.8% ±1.2 pts | 1.7% | – |
| Worked from home | 28.2% ±8.2 pts | 28.7% | – |
| Mean travel time to work | 36.6 min ±8.9 | 28.9 min | – |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) (Data Profile DP03) · Check it at data.census.gov
What census tracts are in Union Mill?
No census tract lies mostly in Union Mill; 4 tracts reach into it (2020 census blocks).
| Tract | Residents, 2020-2024 | Median household income |
|---|---|---|
| Tract 4905.02Fairfax County | 6,478 | $210,197 |
| Tract 4925Fairfax County | 3,962 | $250,000 or more |
| Tract 4921Fairfax County | 6,985 | $250,000 or more |
| Tract 4920Fairfax County | 6,583 | $250,000 or more |
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026); 2020 block assignment files (tract share = share of the tract's census blocks in Union Mill) · Census block assignment files
How does Union Mill compare with other places in Virginia?
Union Mill ranks 1st of 365 places in Virginia with 1,000 or more residents and a reliable estimate, by median household income.
| Measure | Rank | Of |
|---|---|---|
| Population (ACS 2020-2024) | 210th | 374 |
| Residents per square mile | 309th | 374 |
| Median household income | 1st | 365 |
| Per capita income | 9th | 374 |
| Median home value | 12th | 359 |
| Poverty rate | 224th | 263 |
| Bachelor's degree or higher | 42nd | 359 |
| Median age | 49th | 372 |
| Owner-occupied share | 22nd | 368 |
| Work from home | 70th | 286 |
| Travel time to work | 33rd | 372 |
Union Mill's figures with every place in Virginia (CSV)
Every place in Virginia, sortable · Compare Union Mill with other places
Source: PlainCities ranks computed from the American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026) and PEP Vintage 2025 · How ranks are computed
How reliable are the figures for Union Mill?
22 of the 57 figures for Union Mill on this page carry a coefficient of variation over 40% and are marked with a ring: they come from a small sample, so read them as rough.
The American Community Survey samples about one household in eight over five years, so every figure is an estimate with a 90% margin of error (shown under each value). A ring marks an estimate whose coefficient of variation is over 40%. A change is called only when the gap between the two periods is larger than their combined 90% margin (the square root of the sum of the two squared margins), the Census Bureau's test. How to read a margin of error.
Source: American Community Survey 2020-2024 5-year estimates, U.S. Census Bureau (released January 2026): margins of error as published · ACS technical documentation
How these figures are made: methodology and release checks · reading a margin of error · every state · corrections
Not on this page: crime, weather and schools for Union Mill are other agencies' records. Crime: the FBI's Crime Data Explorer · climate: NOAA's U.S. Climate Normals · schools: the National Center for Education Statistics' school search.