Jefferson County, Illinois
County seat: Mount Vernon · Population 36,147 (2025) · 571 sq mi
Jefferson County is the 38th most populous of Illinois's 102 counties, with 36,147 people (2025 estimate). Its county seat is Mount Vernon. It is part of the Southern region, one of the 10 Illinois economic development regions (DCEO). The map shows its 10 cities and towns and the 6 neighboring counties.
Jefferson County facts
- County seat
- Mount Vernon
- Population (2025 estimate)
- 36,147 −2.6% since 2020
- Land area
- 571 sq mi 41st largest of 102
- Water area
- 13 sq mi
- Population density
- 63 per sq mi
- Established
- 1819
- Same name
- One of 25 Jefferson Counties in the US
- Named after
- Thomas Jefferson Founding Father, U.S. president from 1801 to 1809 (1743–1826)
- Largest city
- Mount Vernon 14,187
- Median household income
- $63,118
- Cities and towns
- 10 plus 1 CDPs
- ZIP codes
- 17
- Time zone
- Central
- FIPS code
- 17081
Cities and towns in Jefferson County
Jefferson County has 10 incorporated cities, towns and villages. Populations count the people living inside Jefferson County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| Mount Vernon (county seat) | City | 14,187 | |
| Ina | Village | 1,612 | |
| Woodlawn | Village | 611 | |
| Bluford | Village | 607 | |
| Dix | Village | 456 | |
| Waltonville | Village | 406 | |
| Bonnie | Village | 365 | |
| Belle Rive | Village | 307 | |
| Nason | City | 198 | |
| Centralia | City | 0 | Clinton, Marion and Washington counties |
Unincorporated communities (CDPs)
Census-designated places are communities without their own city government; the county provides their services.
| Community | Population | Also in |
|---|---|---|
| Opdyke | 246 |
ZIP codes in Jefferson County
17 ZIP codes reach into Jefferson County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 62801 also Marion, Clinton and Washington counties
- 62808 also Washington County
- 62810 also Wayne and Hamilton counties
- 62814 also Wayne County
- 62816
- 62830 also Marion County
- 62836 also Franklin County
- 62846
- 62851 also Wayne and Marion counties
- 62864
- 62872
- 62877 also Washington County
- 62883 also Perry and Franklin counties
- 62889 also Marion County
- 62893 also Marion County
- 62894
- 62898
Population of Jefferson County, 2020–2025
Jefferson County shrank by 968 people (−2.6%) between April 2020 and July 2025: 541 more deaths than births and a net loss of 433 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 36,998 |
| 2021 | 36,904 |
| 2022 | 36,458 |
| 2023 | 36,306 |
| 2024 | 36,112 |
| 2025 | 36,147 |
Neighboring counties
- Marion County north · 36,382 people
- Franklin County south · 36,916 people
- Washington County west · 13,564 people
- Wayne County east · 15,882 people
- Hamilton County southeast · 7,859 people
- Perry County southwest · 20,160 people
Printable Jefferson County map
The PDF is a vector file with real text: it prints sharp on Letter paper and you can search it for a town. The PNG is 2400 pixels wide for slides and documents. Both are free to use with a credit to WhichCounty.
- PDF (Letter) (91 KB)
- PNG (2400 px) (67 KB)
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Sources
- Boundaries: U.S. Census Bureau, 2025 Cartographic Boundary Files (1:500,000).
- Population: Census Bureau county and city estimates, Vintage 2025. CDP populations: American Community Survey 2020–2024.
- Places and ZIP codes: Census Bureau 2026 Gazetteer and 2020 ZIP Code Tabulation Area relationship files.
- County seat, founding year and name origin: Wikidata (CC0), checked against state sources.
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