City · Illinois
O'Fallon, Illinois
O'Fallon, city, in St. Clair County, Illinois. O'Fallon had 32,656 residents on July 1, 2025 by the Census Bureau's estimate, up 0.7% since 2020; the 2020 Census counted 32,289 and the ACS 2020-2024 5-year estimates put it at 32,262 (±72). GEOID 1755249.
Residents, July 2025 estimate
32,656
Census Bureau estimate (no margin published)
2020 Census count: 32,289 · ACS 2020-2024: 32,262 ±72
Median household income
$105,982
±$6,723 (90% margin)
Illinois: $83,390
Median home value
$295,700
±$13,884 (90% margin)
Illinois: $263,300
Median gross rent
$1,332
±$114 (90% margin)
Illinois: $1,274
Where is O'Fallon and what county is it in?
O'Fallon is a city in St. Clair County, Illinois. It covers 15.8 square miles of land, 2,043 residents per square mile in 2020.
O'Fallon is in the St. Louis, MO-IL metropolitan statistical area, which takes in 15 counties (Census Bureau delineation, July 2023).
O'Fallon lies mostly within O'Fallon Township and reaches into Caseyville Township and Shiloh Valley Township, towns or townships with their own local government (2020 census blocks).
Source: 2024 Gazetteer and 2020 place-by-county files, U.S. Census Bureau · Census reference files
How many people live in O'Fallon, and is it growing?
The Census Bureau estimates that 32,656 people lived in O'Fallon on July 1, 2025, up 0.7% since 2020, while Illinois shrank 0.8%. The 2020 Census counted 32,289 residents. The 2020-2024 American Community Survey, a five-year sample, puts the population at 32,262 (±72).
| Measure | O'Fallon | St. Clair County | Change since 2015-2019 |
|---|---|---|---|
| Total population | 32,262 ±72 | 253,694 | +2,929 |
| Households | 12,816 ±422 | 100,846 | +1,842 |
| Average household size | 2.52 ±0.08 | 2.47 | −0.15 |
| Housing units | 13,530 ±485 | 115,630 | +1,918 |
O'Fallon's population since 2000
From 21,910 in 2000 to 32,656 in 2025: up 49.0%. The 2000, 2010 and 2020 figures are census counts, each for O'Fallon as it was drawn that year: a place that annexed land, or a community that has since incorporated, covered a different area then. The 2005 figure is the Census Bureau's intercensal estimate, revised to fit the 2000 and 2010 counts and drawn on 2010 boundaries; 2015 and 2025 are July 1 estimates made from the census before them.
Source: The 2000, 2010 and 2020 Census counts and the Census Bureau's population estimates (intercensal 2000-2010, Vintage 2020, Vintage 2025) · Census population estimates
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 O'Fallon?
The median resident of O'Fallon is 37.8 years old; 26.2% are under 18 and 16.7% are 65 or older. The largest group is non-Hispanic white residents at 69.4%, then non-Hispanic Black residents at 16.5%. 3.8% of residents were born outside the United States.
| Measure | O'Fallon | St. Clair County | Change since 2015-2019 |
|---|---|---|---|
| Median age | 37.8 ±1.5 | 39.9 | no clear change |
| Under 18 years | 26.2% ±1.6 pts | 23.0% | – |
| 65 years and over | 16.7% ±1.5 pts | 17.3% | – |
| Male | 49.5% ±1.7 pts | 48.5% | – |
| Hispanic or Latino (any race) | 5.1% ±1.3 pts | 5.1% | no clear change |
| White alone, not Hispanic | 69.4% ±2.4 pts | 59.1% | −7.0 pts |
| Black or African American alone, not Hispanic | 16.5% ±2.2 pts | 27.7% | +4.9 pts |
| Asian alone, not Hispanic | 2.6% ±0.7 pts | 1.6% | no clear change |
| American Indian and Alaska Native alone, not Hispanic | 0.1% ±0.1 pts | 0.2% | – |
| Native Hawaiian and Other Pacific Islander alone, not Hispanic | 0.0% ±0.1 pts | 0.0% | – |
| Two or more races, not Hispanic | 5.8% ±1.9 pts | 5.8% | – |
| Some other race alone, not Hispanic | 0.4% ±0.5 pts | 0.5% | – |
| Born outside the United States | 3.8% ±1.3 pts | 3.3% | no clear change |
| Speak a language other than English at home (age 5+) | 5.2% ±1.7 pts | 5.0% | – |
| Civilian veterans (age 18+) | 20.2% ±2.0 pts | 11.5% | – |
| With a disability | 10.8% ±1.8 pts | 15.2% | – |
| No health insurance coverage | 4.0% ±1.2 pts | 5.1% | no clear change |
| High school graduate or higher (age 25+) | 97.6% ±0.8 pts | 93.5% | – |
| Bachelor's degree or higher (age 25+) | 52.4% ±2.9 pts | 31.8% | +4.6 pts |
| Graduate or professional degree (age 25+) | 23.4% ±2.2 pts | 13.8% | – |
| Lived in the same house a year earlier | 88.2% ±2.4 pts | 88.3% | – |
| Moved from another state in the past year | 3.1% ±0.9 pts | 3.0% | – |
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 O'Fallon earn?
Half of O'Fallon's 12,816 households earn less than $105,982 a year (±$6,723), against $73,854 in St. Clair County and $83,390 in Illinois. In 2015-2019 it was $111,192 in 2024 dollars; the margins of error cannot tell the two periods apart. 6.2% of residents live below the poverty line.
| Measure | O'Fallon | St. Clair County | Change since 2015-2019 |
|---|---|---|---|
| Median household income | $105,982 ±$6,723 | $73,854 | no clear change |
| Mean household income | $136,093 ±$6,759 | $96,049 | – |
| Per capita income | $54,265 ±$2,797 | $38,942 | +$5,274 |
| People below the poverty line | 6.2% ±2.3 pts | 13.6% | no clear change |
| Children under 18 below the poverty line | 10.0% ±5.3 pts | 18.9% | no clear change |
| Households receiving SNAP | 7.8% ±1.8 pts | 16.2% | – |
| Households with a computer | 97.6% ±0.8 pts | 94.2% | – |
| Households with a broadband subscription | 94.5% ±2.2 pts | 89.7% | – |
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 O'Fallon?
Owners occupy 70.2% of O'Fallon's occupied homes and renters 29.8%. The median owner-occupied home is valued at $295,700 by its owner (±$13,884). The median renter pays $1,332 a month including utilities, and 42.9% of renters pay 35% or more of their income on rent.
| Measure | O'Fallon | St. Clair County | Change since 2015-2019 |
|---|---|---|---|
| Median home value (owner-occupied) | $295,700 ±$13,884 | $180,300 | +$39,839 |
| Median gross rent | $1,332 ±$114 | $1,090 | no clear change |
| Renters paying 35% or more of income on rent | 42.9% ±8.7 pts | 39.8% | +16.5 pts |
| Median monthly owner costs, with a mortgage | $2,105 ±$98 | $1,645 | – |
| Owner-occupied homes | 70.2% ±3.3 pts | 68.4% | no clear change |
| Renter-occupied homes | 29.8% ±3.3 pts | 31.6% | – |
| Housing units | 13,530 ±485 | 115,630 | +1,918 |
| Homeowner vacancy rate | 1.8% ±1.5 pts | 1.1% | – |
| Rental vacancy rate | 3.5% ±2.4 pts | 4.7% | – |
| Single-family detached homes | 66.6% ±2.8 pts | 72.1% | – |
| Mobile homes | 3.1% ±1.2 pts | 4.4% | – |
| Built 2020 or later | 2.5% ±1.1 pts | 0.9% | – |
| Built 2010 to 2019 | 17.8% ±3.5 pts | 7.3% | – |
| Built 1939 or earlier | 5.4% ±1.5 pts | 13.5% | – |
| Households with no vehicle | 5.9% ±2.2 pts | 7.5% | – |
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 many new homes is O'Fallon building?
Builders took permits for 200 new housing units in O'Fallon in 2025 (72 in single-family houses), 6.1 per 1,000 residents against 1.5 across Illinois.
Counts of units in permits a local office issued; not every permitted unit is built. A year marked with months was reported for part of the year.
Source: Building Permits Survey, annual place files 2019-2025, U.S. Census Bureau · Census Building Permits Survey
How do people in O'Fallon work and get to work?
70.5% of O'Fallon's workers drive alone and 20.4% work from home. The average trip to work takes 25.3 minutes. The unemployment rate in 2020-2024 averaged 3.7%.
| Measure | O'Fallon | St. Clair County | Change since 2015-2019 |
|---|---|---|---|
| In the labor force (age 16+) | 65.8% ±2.3 pts | 63.4% | – |
| Unemployment rate | 3.7% ±1.1 pts | 6.0% | no clear change |
| Drove alone to work | 70.5% ±3.2 pts | 75.4% | – |
| Carpooled | 6.1% ±1.9 pts | 8.1% | – |
| Public transportation | 0.5% ±0.3 pts | 1.6% | – |
| Walked | 2.2% ±1.9 pts | 1.5% | – |
| Worked from home | 20.4% ±3.1 pts | 12.4% | +16.0 pts |
| Mean travel time to work | 25.3 min ±2.8 | 24.0 min | no clear change |
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 O'Fallon?
6 census tracts lie mostly in O'Fallon, and 6 more reach into it (2020 census blocks). Their median household incomes run from $74,348 (Tract 5043.54) to $179,261 (Tract 5043.53).
| Tract | Residents, 2020-2024 | Median household income |
|---|---|---|
| Tract 5043.54St. Clair County | 6,755 | $74,348 |
| Tract 5034.14St. Clair County | 5,570 | $77,733 |
| Tract 5043.55St. Clair County | 5,193 | $143,333 |
| Tract 5043.52St. Clair County | 4,055 | $79,112 |
| Tract 5043.51St. Clair County | 3,293 | $134,650 |
| Tract 5043.53St. Clair County | 4,286 | $179,261 |
| Tract 5034.04St. Clair County | 8,854 | $161,276 |
| Tract 5039.08St. Clair County | 6,774 | $106,129 |
| Tract 5039.07St. Clair County | 4,983 | $89,189 |
| Tract 5043.58St. Clair County | 3,677 | $81,856 |
| Tract 5038St. Clair County | 1,258 | $168,700 |
| Tract 5043.59St. Clair County | 4,338 | $90,329 |
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 O'Fallon) · Census block assignment files
How does O'Fallon compare with other places in Illinois?
By the Census Bureau's July 2025 estimates, O'Fallon is the 1,261st-most populous of the 19,476 U.S. incorporated places that have one and the 59th-most populous of 1,294 in Illinois.
O'Fallon ranks 274th of 1,380 places in Illinois with 1,000 or more residents and a reliable estimate, by median household income.
| Measure | Rank | Of |
|---|---|---|
| Population, July 2025 estimate | 59th | 1,294 |
| Growth 2020-2025 (PEP) | 202nd | 1,347 |
| Residents per square mile | 268th | 1,383 |
| Median household income | 274th | 1,380 |
| Per capita income | 178th | 1,383 |
| Median home value | 258th | 1,379 |
| Median gross rent | 286th | 1,280 |
| Poverty rate | 868th | 1,119 |
| Bachelor's degree or higher | 124th | 1,369 |
| Median age | 1,067th | 1,383 |
| Owner-occupied share | 1,028th | 1,382 |
| Work from home | 144th | 1,015 |
| Travel time to work | 720th | 1,382 |
O'Fallon's figures with every place in Illinois (CSV)
Every place in Illinois, sortable · Compare O'Fallon 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 O'Fallon?
6 of the 57 figures for O'Fallon 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 O'Fallon 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' public schools in O'Fallon.