Williamson County, Illinois
County seat: Marion · Population 67,225 (2025) · 420 sq mi
Williamson County is the 22nd most populous of Illinois's 102 counties, with 67,225 people (2025 estimate). Its county seat is Marion. It is part of the Southern region, one of the 10 Illinois economic development regions (DCEO). The map shows its 16 cities and towns and the 5 neighboring counties.
Williamson County facts
- County seat
- Marion
- Population (2025 estimate)
- 67,225 +0.1% since 2020
- Land area
- 420 sq mi 68th largest of 102
- Water area
- 24 sq mi
- Population density
- 160 per sq mi
- Established
- 1839
- Same name
- One of 3 Williamson Counties in the US
- Named after
- Hugh Williamson American politician (1735-1819)
- Largest city
- Marion 17,148
- Median household income
- $65,604
- Cities and towns
- 16 plus 3 CDPs
- ZIP codes
- 22
- Time zone
- Central
- FIPS code
- 17199
Cities and towns in Williamson County
Williamson County has 16 incorporated cities, towns and villages. Populations count the people living inside Williamson County; cities that cross a county line also list the other counties.
| Name | Type | Population 2025 | Also in |
|---|---|---|---|
| Marion (county seat) | City | 17,148 | |
| Herrin | City | 12,268 | |
| Carterville | City | 5,839 | |
| Johnston City | City | 3,313 | |
| Cambria | Village | 1,796 | |
| Crainville | Village | 1,507 | |
| Energy | Village | 960 | |
| Hurst | City | 751 | |
| Pittsburg | Village | 561 | |
| Creal Springs | City | 491 | |
| Bush | Village | 236 | |
| Spillertown | Village | 188 | |
| Colp | Village | 175 | |
| Freeman Spur | Village | 152 | Franklin County |
| Stonefort | Village | 119 | Saline County |
| Carbondale | City | 0 | Jackson County |
Unincorporated communities (CDPs)
Census-designated places are communities without their own city government; the county provides their services.
| Community | Population | Also in |
|---|---|---|
| Crab Orchard | 394 | |
| Whiteash | 301 | |
| Blairsville | 231 |
ZIP codes in Williamson County
22 ZIP codes reach into Williamson County. ZIP codes ignore county lines, so some also cover a neighboring county.
- 62841
- 62890 also Franklin, Hamilton and Saline counties
- 62896 also Franklin County
- 62901 also Jackson County
- 62902 also Jackson and Union counties
- 62915
- 62917 also Saline County
- 62918 also Jackson County
- 62921
- 62922 also Johnson County
- 62924 also Jackson County
- 62933
- 62935 also Saline and Hamilton counties
- 62939 also Johnson and Union counties
- 62948
- 62949
- 62951
- 62958 also Jackson and Union counties
- 62959
- 62967 also Johnson County
- 62974
- 62987 also Pope and Saline counties
Population of Williamson County, 2020–2025
Williamson County grew by 62 people (+0.1%) between April 2020 and July 2025: 1,035 more deaths than births and a net gain of 1,048 people from migration.
| Year (July 1) | Population |
|---|---|
| 2020 | 67,127 |
| 2021 | 66,910 |
| 2022 | 66,544 |
| 2023 | 66,749 |
| 2024 | 67,074 |
| 2025 | 67,225 |
Neighboring counties
- Franklin County north · 36,916 people
- Johnson County south · 13,363 people
- Saline County east · 22,772 people
- Jackson County west · 52,501 people
- Union County southwest · 16,656 people
Printable Williamson 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) (98 KB)
- PNG (2400 px) (65 KB)
Paste this code to embed the map on your site:
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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