How many people live in Mercer County, IL?
Updated Apr. 6, 2026Refreshed annually
In 2024, there were about 15,300 people living in Mercer County, IL. That makes Mercer County the 70th-most populous county in Illinois. It is home to 0.12% of people living in the state.
15.3K
population of Mercer County, IL (2024)
0.12%
County share of the Illinois population (2024)
About 15,300 people lived in Mercer County, IL in 2024.
Population estimates, 2000–2024
What are Mercer County, IL’s age demographics?
About 3,500 Mercer County residents are aged 65 and older in 2024. That represents 22.8% of its population. For comparison, the age group represents 17.9% of Illinois' population and 18% in the US overall.
Another 3,200 Mercer County residents, or 20.6% 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 higher share of Mercer County, IL's population is aged 65 or older than the US as a whole.
Population estimates by age group, (2024)
What are Mercer County, IL’s racial and ethnic demographics?
Non-Hispanic white residents make up 93.3% of the Mercer County, IL population, higher than the national share of 57.5%.
In contrast, Mercer County’s Hispanic population accounts for 3.8%, below the 20% nationwide, and the non-Hispanic Black or African American population makes up 0.94% 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.
Mercer 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 Mercer County, IL is Aledo with about 3,500 residents in 2024.
Cities and towns in Mercer County, IL ranked by population
Population (2024), includes only portions within county
| City or town | Population | |
|---|---|---|
| 1. | Aledo | 3,522 |
| 2. | Viola | 843 |
| 3. | Matherville | 690 |
| 4. | Sherrard | 688 |
| 5. | Windsor | 652 |
| 6. | New Boston | 605 |
| 7. | Keithsburg | 545 |
| 8. | Eliza | 401 |
| 9. | Joy | 359 |
| 10. | Alexis (pt.) | 304 |
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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.
