| Name | Jefferson County |
| State | Illinois |
| FIPS Code | 17081 |
| County Seat | Mount Vernon |
| Timezone | Central Daylight Time (CDT) |
| Population (2022) | 38,908 |
| Population Growth Rate(2000-2022) | -4.41% |
| Majority Ethnicity | White 91.61% |
| Public School Majority Ethnicity | White 75% |
| Partisan Voting Index | Strongly Republican:+24 |
| Unemployment Rate (February 2025) | 4.1% |
| Area Code(s) | 618 |
| Race/Ethnicity | Percentage of Population (2022) |
|---|---|
| White | 91.61% |
| African American | 6.96% |
| Hispanic | 0.25% |
| Asian | 1.14% |
| Native American | 0.02% |
| Hawaiin/Pacific Islander | 0.02% |
| Race/Ethnicity | Percentage of Public School Students (2023) |
|---|---|
| White | 75.34% |
| African American | 12.38% |
| Hispanic | 3.23% |
| Asian | 0.71% |
| Native American | 0.06% |
| Hawaiin/Pacific Islander | 0.02% |