How many people live in St. Charles County, MO?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 423,700 people living in St. Charles County, MO. That makes St. Charles County the third-most populous county in Missouri. It is home to 6.8% of people living in the state.
424K
population of St. Charles County, MO (2024)
6.8%
County share of the Missouri population (2024)
About 423,700 people lived in St. Charles County, MO in 2024.
Population estimates, 2000–2024
What are St. Charles County, MO’s age demographics?
About 76,900 St. Charles County residents are aged 65 and older in 2024. That represents 18.1% of its population. For comparison, the age group represents 18.8% of Missouri’s population and 18% in the US overall.
Another 92,600 St. Charles County residents, or 21.9% of the population, were children under 18. For comparison, the age group represents 22% of Missouri’s population and 21.6% in the US overall.
A lower share of St. Charles County, MO's population is aged 18–24 than the US as a whole.
Population estimates by age group, (2024)
What are St. Charles County, MO’s racial and ethnic demographics?
Non-Hispanic white residents make up 82.9% of the St. Charles County, MO population, higher than the national share of 57.5%.
In contrast, St. Charles County’s Hispanic population accounts for 4.5%, below the 20% nationwide, and the non-Hispanic Black or African American population makes up 6.4% of the county, compared with 12.6% nationally.
Racial and ethnic make up differ based on location. These figures reflect how people identified their race alone (not in combination with other races), and separate out Hispanic or Latino ethnicity, following Census reporting standards.
St. Charles County, MO has a higher share of a non-Hispanic white population than Missouri as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in St. Charles County, MO is O'Fallon with about 95,400 residents in 2024.
Cities and towns in St. Charles County, MO ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | O'Fallon | 95,355 |
| 2. | St. Charles | 72,458 |
| 3. | St. Peters | 61,398 |
| 4. | Wentzville | 48,646 |
| 5. | Lake St. Louis | 19,160 |
| 6. | Dardenne Prairie | 14,407 |
| 7. | Cottleville | 6,378 |
| 8. | Weldon Spring | 5,304 |
| 9. | St. Paul | 3,725 |
| 10. | Flint Hill | 561 |
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Methodology
USAFacts standardizes data, in areas such as time and demographics, to make it easier to understand and compare.
The analysis was generated with the help of AI and reviewed by USAFacts for accuracy.
Page sources
USAFacts endeavors to share the most up-to-date information available. We sourced the data on this page directly from government agencies; however, the intervals at which agencies publish updated data vary.
