O'Fallon, Illinois Demographics
Population trends, housing costs, income, commuting, and health, all on one page.
O'Fallon, IL Population Density Map and Area Scores
Area Score
Health, income and education, each graded from F to A+. Explore interactive maps for deeper analysis.
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A
Health Above average
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B
Income Around average
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A+
Education Top grade
Source: Map AI Methodology
Population
| Metric | O'Fallon | Illinois Avg | U.S. Average |
|---|---|---|---|
| Population | 21,856 | 12,692,444 | 337,468,954 |
| Population density (per sq mi) | 1373.4 | 219.1 | 86.4 |
| Population growth (%/yr) | 0.97% | -0.16% | 0.59% |
| Median age | 35.1 | 37.4 | 37.3 |
| Households | 8,982 | 5,035,584 | 130,235,071 |
Population in O'Fallon grew by 7.4% from 2009 to 2024, reaching 21,856 in 2024.
Population Growth 2009–2024
Race & Ethnicity
Age & Sex
The largest generation in O'Fallon is Millennials, aged 29–44, at 23.6% of residents. That is 1.7 points above Illinois as a whole.
- Gen Z 13–28 4,295 19.7% -1.6 pts
- Millennials 29–44 5,164 23.6% +1.7 pts
- Gen X 45–60 4,223 19.3% -1.1 pts
- Boomers 61–79 3,298 15.1% -1.8 pts
Residents by birth cohort, from the 2025 age distribution. The right-hand figure is how far each cohort's share sits above or below Illinois, in percentage points. Children younger than Gen Z and the generations before the Boomers are counted in the population but not shown here, so these shares do not add up to 100%.
Male and female share
Women are 51.2% of the people living in O'Fallon and men 48.8%.
- Women 51.2% Illinois 50.6%
- Men 48.8% Illinois 49.4%
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Economy
O'Fallon has a the economy index of B, which means it is quite prosperous.
| Metric | O'Fallon | Illinois Avg | U.S. Average |
|---|---|---|---|
| Median household income | $93,422 | $84,042 | $80,455 |
| Income growth (%/yr) | 3.44% | 4.46% | 4.80% |
| Unemployment rate | 3.2% | 5.8% | 5.2% |
The median household income in O'Fallon is about 11% higher than in Illinois.
Housing
| Metric | O'Fallon | Illinois Avg | U.S. Average |
|---|---|---|---|
| Median home price | $22,592 | $149,936 | $248,835 |
| Median rent | $1,372 | $1,274 | $1,407 |
| Homeownership rate | 64.7% | 67.1% | 65.2% |
The median home price in O'Fallon is about 1.4 years' worth of rent — buying at the median price costs roughly as much as paying the median rent of $1,372 per month for that long.
Commute Time & Mobility
Commuters in O'Fallon spend about 41 minutes on the road round trip each working day. Over a typical 250-day work year, that adds up to roughly 172 hours, about 7.1 full days, spent commuting.
| Metric | O'Fallon | Illinois Avg | U.S. Average |
|---|---|---|---|
| One-way commute (min) | 20.6 | 23.6 | 22.4 |
| Round-trip commute (min) | 41.2 | 47.3 | 44.8 |
| Yearly time spent (hours) | 172 | 197 | 187 |
| Estimated yearly cost | $5,319 | $6,104 | $5,790 |
| Work from home | 16.8% | 15.9% | 15.0% |
| Highway traffic (vehicles/day) | 14,756 | 7,977 | 8,813 |
| Local road traffic (vehicles/day) | 2,394 | 1,547 | 1,355 |
The average commute time in O'Fallon is 21 minutes, shorter than the 24 minutes in Illinois.
Estimated yearly cost applies a single national wage rule of thumb (U.S. Bureau of Labor Statistics average hourly earnings), not a measurement of wages in this area. Traffic volume figures come from proprietary Ticon and TrafficZoom data.
Education & Households
O'Fallon has a education index of A+, which means it is exceptionally educated.
| Metric | O'Fallon | Illinois Avg | U.S. Average |
|---|---|---|---|
| Bachelor's degree or higher | 42.0% | 34.1% | 31.6% |
| Average household size | 2.43 | 2.46 | 2.53 |
Health
O'Fallon has a health index of A, which means it is very healthy.
| Metric | O'Fallon | Illinois Avg | U.S. Average |
|---|---|---|---|
| Life expectancy (years) | 78.8 | 77.9 | 78.3 |
| Self-rated poor health | 10.3% | 15.6% | 16.3% |
| Smokers | 13.3% | 19.2% | 19.0% |
Frequently Asked Questions
Common questions about O'Fallon, Illinois.
What is the population of O'Fallon, Illinois?
About 21,856 people live in O'Fallon, Illinois, in 8,982 households of 2.4 people on average. The median age is 35.1, so residents are younger than the U.S. median of 37.3 by about 2 years.
How densely populated is O'Fallon, Illinois?
Averaged over its land area, O'Fallon, Illinois has 1,373 people per square mile, a density typical of urban and suburban areas. That is about 16 times the U.S. average of 86.
Can a typical household afford a home in O'Fallon, Illinois?
The median home costs 0.2 times the median household income ($22,592 against $93,422), compared with 3.1 times nationally. That is within the traditional rule of thumb of about 3 times income. Median rent of $1,372 a month takes about 18% of the median household's income, below the 30% level at which HUD considers renters cost-burdened.
Is unemployment high in O'Fallon, Illinois?
Unemployment in O'Fallon, Illinois is only 3.2%, well below the U.S. rate of 5.2%, a sign of a tight labor market where employers compete for workers.
How common is a college degree in O'Fallon, Illinois?
42.0% of adults in O'Fallon, Illinois hold a bachelor's degree or higher (about 1 in 2), well above the U.S. share of 31.6%.
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