How many people live in Marion County, IL?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 36,400 people living in Marion County, IL. That makes Marion County the 37th-most populous county in Illinois. It is home to 0.29% of people living in the state.
36.4K
population of Marion County, IL (2024)
0.29%
County share of the Illinois population (2024)
About 36,400 people lived in Marion County, IL in 2024.
Population estimates, 2000–2024
What are Marion County, IL’s age demographics?
About 7,600 Marion County residents are aged 65 and older in 2024. That represents 20.8% of its population. For comparison, the age group represents 17.9% of Illinois' population and 18% in the US overall.
Another 8,400 Marion County, IL residents, or 23.2% of the population, were children under 18. For comparison, the age group represents 21.2% of Illinois’s population and 21.6% in the US overall.
A lower share of Marion County, IL's population is aged 25–44 than the US as a whole.
Population estimates by age group, (2024)
What are Marion County, IL’s racial and ethnic demographics?
Non-Hispanic white residents make up 90.1% of the Marion County, IL population, higher than the national share of 57.5%.
In contrast, Marion County’s Hispanic population accounts for 2.3%, below the 20% nationwide, and the non-Hispanic Black or African American population makes up 4.4% 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.
Marion County, IL has a higher share of a non-Hispanic white population than Illinois as a whole.
Population estimates by race and ethnicity, (2024)
The largest city or town in Marion County, IL is Centralia with about 9,600 residents in 2024.
Cities and towns in Marion County, IL ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Centralia (pt.) | 9,637 |
| 2. | Salem (pt.) | 6,960 |
| 3. | Raccoon | 1,498 |
| 4. | Stevenson | 1,141 |
| 5. | Sandoval | 1,125 |
| 6. | Central City | 1,067 |
| 7. | Odin | 903 |
| 8. | Kinmundy | 711 |
| 9. | Junction City | 523 |
| 10. | Patoka | 508 |
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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.
