O'Fallon Flag

O'Fallon

County Seat:
No
Area (mi²):
15.791
State:
Illinois

O'Fallon is a city located in St. Clair County, Illinois. O'Fallon has a 2025 population of 32,108 . O'Fallon is currently declining at a rate of -0.19% annually and its population has decreased by -0.94% since the most recent census, which recorded a population of 32,413 in 2020.

The average household income in O'Fallon is $131,945 with a poverty rate of 4.39%. The median age in O'Fallon is 36.9 years: 35.1 years for males, and 38.2 years for females. For every 100 females there are 97.5 males.

32.1K
Total Population
2,033
Density (mi²)
-61 -0.19%
Growth

O'Fallon Population

Demographics

Economics and Income Statistics

Sources

  1. US Census State Population Estimates - Most recent state estimates from the Census Bureau's Population Estimates Program
  2. US Census County Population Estimates - Most recent county estimates from the Census Bureau's Population Estimates Program
  3. American Community Survey (2009 - 2013)
  4. Census QuickFacts
  5. Historical Populations of States and Counties (1790 - 1990)