Jefferson County IL United States
| County FIPS | 17081 |
| Largest City | Mount Vernon |
| State | Illinois |
| Latitude | 38.3005 |
| Longitude | -88.9240 |
| Population | 36,550 |
| Density | 63.99 people per square mile |
| Time Zone | America/Chicago |
Median household: $63,118
Median individual: $36,579
Mode: 84.0% White
Median house value: $124,847.0
Median: 41.2 years old
With at least college degree: 18.1%
With STEM degree: 38.8%
Never married: 28.5%
Unemployed: 5.8%
All data comes from the SimpleMaps US Counties Database, 2026.
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