| Name | Williamson County |
| State | Illinois |
| FIPS Code | 17199 |
| County Seat | Marion |
| Timezone | Central Daylight Time (CDT) |
| Population (2024) | 66,737 |
| Population Growth Rate(2020-2024) | -0.62% |
| Majority Ethnicity | White 91.47% |
| Public School Majority Ethnicity | White 81% |
| Partisan Voting Index | Republican:+20 |
| Unemployment Rate (May 2026) | 5.0% |
| Sales Tax Rate (2025) | 9.5% |
| Area Code(s) | 618 |
| Race/Ethnicity | Percentage of Population (2023) |
|---|---|
| White | 91.47% |
| African American | 3.57% |
| Hispanic | 2.88% |
| Asian | 1.6% |
| Native American | 0.47% |
| Hawaiin/Pacific Islander | 0% |
| Race/Ethnicity | Percentage of Public School Students (2023) |
|---|---|
| White | 80.92% |
| African American | 5.83% |
| Hispanic | 4.62% |
| Asian | 1.18% |
| Native American | 0.17% |
| Hawaiin/Pacific Islander | 0.03% |