County in Illinois
Jefferson County
About 36,600 people, median household income $63,100.
Who lives in Jefferson County
Census survey estimates for 2020 to 2024, rounded.
People
- Population
- 36,600
- Median age
- 41.2 years
- Under 18
- 22%
- 65 and over
- 20%
- Veterans, of adults
- 8%
- Speak another language at home
- 4%
Race and ethnicity
- Hispanic or Latino, of any race
- 3%
- White, not Hispanic
- 84%
- Black, not Hispanic
- 6%
- Asian, not Hispanic
- 1%
Income and housing
- Median household income
- $63,100
- Below the poverty line
- 14%
- Bachelor's or higher, adults 25+
- 18%
- Owner-occupied homes
- 72%
- Median home value
- $126,000
2024 vote for president
- Donald Trump, Republican
- 73.2%
- Kamala Harris, Democrat
- 25.4%
- Other candidates
- 1.4%
Votes counted, by precinct. Source: MIT Election Data and Science Lab, precinct returns (public domain).
Represent all of Jefferson County
Jefferson County's districts
U.S. House District 12
All of Jefferson County
Held by Mike Bost, Republican
- Washington office: (202) 225-5661
About 746,800 people, median household income $68,500.
Largest towns: O'Fallon (part), Carbondale, Marion and 281 more
Illinois Senate District 58
All of Jefferson County
Held by Terri Bryant, Republican
- Springfield office: (217) 782-8137
- District office: (618) 684-1100
About 214,600 people, median household income $66,100.
Largest towns: Mount Vernon, Waterloo, Columbia (part) and 85 more
Illinois House District 116
All of Jefferson County
Held by Dave Severin, Republican
- Springfield office: (217) 782-1051
- District office: (618) 440-5090
About 106,900 people, median household income $58,500.
Largest towns: Mount Vernon, Mount Carmel, Benton and 46 more
Source: U.S. Census Bureau, American Community Survey 5-year estimates, 2020–2024; towns and counties from the 2020 Census, 119th Congressional District and 2024 state legislative district tabulation. Figures rounded by us. Retrieved 2026-10-19. This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.
Towns (11)
Cities, villages and unincorporated communities, with the number of people in the county’s part of each at the 2020 Census.
- Mount Vernon14,600
- Ina1,641
- Bluford630
- Woodlawn617
- Dix469
- Waltonville408
- Bonnie374
- Belle Rive309
- Opdyke236
- Nason199
- Centralia (part)0
Source: U.S. Census Bureau, American Community Survey 5-year estimates, 2020–2024; towns and counties from the 2020 Census, Demographic and Housing Characteristics. Figures rounded by us. Retrieved 2026-10-19. This product uses the Census Bureau Data API but is not endorsed or certified by the Census Bureau.