Marion County, Illinois
County seat: Salem · Population 36,382 (2025) · 573 sq mi
Marion County is the 37th most populous of Illinois's 102 counties, with 36,382 people (2025 estimate). Its county seat is Salem. It is part of the Southeast region, one of the 10 Illinois economic development regions (DCEO). The map shows its 15 cities and towns and the 6 neighboring counties.
Marion County facts
- County seat
- Salem
- Population (2025 estimate)
- 36,382 −3.6% since 2020
- Land area
- 573 sq mi 40th largest of 102
- Water area
- 4 sq mi
- Population density
- 64 per sq mi
- Established
- 1823
- Same name
- One of 17 Marion Counties in the US
- Named after
- Francis Marion American politician, Continental Army officer (1732-1795)
- Largest city
- Centralia 9,598 in the county
- Median household income
- $61,240
- Cities and towns
- 15
- ZIP codes
- 15
- Time zone
- Central
- FIPS code
- 17121
Cities and towns in Marion County
Marion County has 15 incorporated cities, towns and villages. Populations count the people living inside Marion County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| Centralia | City | 9,598 | Clinton, Jefferson and Washington counties |
| Salem (county seat) | City | 7,035 | |
| Sandoval | Village | 1,123 | |
| Central City | Village | 1,067 | |
| Odin | Village | 903 | |
| Kinmundy | City | 702 | |
| Junction City | Village | 517 | |
| Patoka | Village | 507 | |
| Iuka | Village | 491 | |
| Wamac | City | 395 | Clinton and Washington counties |
| Alma | Village | 302 | |
| Kell | Village | 169 | |
| Vernon | Village | 97 | |
| Walnut Hill | Village | 92 | |
| Farina | Village | 0 | Fayette County |
ZIP codes in Marion County
15 ZIP codes reach into Marion County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 62801 also Clinton, Washington and Jefferson counties
- 62807
- 62830 also Jefferson County
- 62838 also Fayette, Clay and Effingham counties
- 62849
- 62851 also Wayne and Jefferson counties
- 62853
- 62854 also Clay and Fayette counties
- 62870
- 62875 also Fayette and Clinton counties
- 62881
- 62882 also Clinton County
- 62889 also Jefferson County
- 62892 also Fayette County
- 62893 also Jefferson County
Population of Marion County, 2020–2025
Marion County shrank by 1,358 people (−3.6%) between April 2020 and July 2025: 757 more deaths than births and a net loss of 603 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 37,656 |
| 2021 | 37,383 |
| 2022 | 36,860 |
| 2023 | 36,660 |
| 2024 | 36,501 |
| 2025 | 36,382 |
Neighboring counties
- Fayette County north · 20,790 people
- Jefferson County south · 36,147 people
- Clinton County west · 37,128 people
- Clay County east · 12,793 people
- Wayne County southeast · 15,882 people
- Washington County southwest · 13,564 people
Printable Marion 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) (93 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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