Williamson County IL United States
| County FIPS | 17199 |
| Largest City | Marion |
| State | Illinois |
| Latitude | 37.7303 |
| Longitude | -88.9299 |
| Population | 66,876 |
| Density | 159.2 people per square mile |
| Time Zone | America/Chicago |
Median household: $65,604
Median individual: $38,946
Mode: 89.0% White
Median house value: $151,257.0
Median: 41.6 years old
With at least college degree: 26.3%
With STEM degree: 40.9%
Never married: 27.4%
Unemployed: 5.0%
All data comes from the SimpleMaps US Counties Database, 2026.
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