| Name | Johnson County |
| State | Illinois |
| FIPS Code | 17087 |
| County Seat | Vienna |
| Timezone | Central Daylight Time (CDT) |
| Population (2024) | 13,355 |
| Population Growth Rate(2020-2024) | 0.36% |
| Majority Ethnicity | White 87.2% |
| Public School Majority Ethnicity | White 94% |
| Partisan Voting Index | Strongly Republican:+30 |
| Unemployment Rate (May 2026) | 5.9% |
| Sales Tax Rate (2025) | 7.75% |
| Area Code(s) | 618 |
| Race/Ethnicity | Percentage of Population (2023) |
|---|---|
| White | 87.2% |
| African American | 8.03% |
| Hispanic | 4.51% |
| Asian | 0.26% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 0% |
| Race/Ethnicity | Percentage of Public School Students (2023) |
|---|---|
| White | 93.98% |
| African American | 0.64% |
| Hispanic | 1.83% |
| Asian | 0.32% |
| Native American | 0% |
| Hawaiin/Pacific Islander | 0% |