How many people live in Jefferson County, MO?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 231,900 people living in Jefferson County, MO. That makes Jefferson County the seventh-most populous county in Missouri. It is home to 3.7% of people living in the state.
232K
population of Jefferson County, MO (2024)
3.7%
County share of the Missouri population (2024)
About 231,900 people lived in Jefferson County, MO in 2024.
Population estimates, 2000–2024
What are Jefferson County, MO’s age demographics?
About 41,400 Jefferson County, MO residents are aged 65 and older in 2024. That represents 17.9% of its population. For comparison, the age group represents 18.8% of Missouri’s population and 18% in the US overall.
Another 50,700 Jefferson County residents, or 21.8% 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 higher share of Jefferson County, MO's population is aged 45–64 than the US as a whole.
Population estimates by age group, (2024)
What are Jefferson County, MO’s racial and ethnic demographics?
Non-Hispanic white residents make up 92.6% of the Jefferson County, MO population, higher than the national share of 57.5%.
In contrast, Jefferson County’s Hispanic population accounts for 2.8%, below the 20% nationwide, and the non-Hispanic Black or African American population makes up 1.4% 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.
Jefferson 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 Jefferson County, MO is Arnold with about 21,000 residents in 2024.
Cities and towns in Jefferson County, MO ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Arnold | 21,036 |
| 2. | Festus | 13,730 |
| 3. | De Soto | 6,503 |
| 4. | Pevely | 6,103 |
| 5. | Herculaneum | 5,321 |
| 6. | Crystal City | 4,703 |
| 7. | Hillsboro | 3,489 |
| 8. | Byrnes Mill | 3,189 |
| 9. | Olympian Village | 712 |
| 10. | Lake Tekakwitha | 236 |
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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.
