Williamson County, Illinois
Williamson County: county in Illinois, United States
About
Williamson County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 66,357 and a population density of 149 people per km². After 10 years in 2020 county had an estimated population of 66,415 inhabitants. Its county seat is Marion. The county was created 187 years ago in 1839.
County Snapshot
Williamson County at a glance
Williamson County currently has 16 quality-checked populated place pages linked on MapSof, making it easier to jump from the county overview into local city pages.
Mapped populated places
16
These counts use a stricter populated-place filter so the main lists stay focused on real city and town pages.
Illinois counties
102
Open related pagesLargest city
MarionPopulation 17,803
Top linked places
Quick Facts about Williamson County
| Population | 66,415 (2020) |
| Country | United States of America |
| State | Illinois (United States) |
| Different from | Williamson County, Williamson County |
| Area | 444 km2 |
| Water as percent of area | 5.4% |
| Land as percent of area | 94.6% |
| Latitude & Longitude | 37.7303,-88.9299 |
| Named for | Hugh Williamson |
| Capital | Marion |
| Establishment | February 28, 1839 |
| Time Zone | America/Chicago |
| Local time | 21:07:15 (18th April 2026) |
| Density | 150 Pop. per km² as of 2020 |
| Population growth | 0.09% (2010-2020) |
| Weather | 74℉ Chance Showers And Thunderstorms 7-days weather |
Geography
Williamson County is located at 37°43'49"N 88°55'48"W (37.7302500, -88.9299400). It has 6 neighbors: Franklin County, Jackson County, Johnson County, Pope County, Saline County and Union County.
Williamson County map
icon to open full mode. View satellite images
The largest city of Williamson County is Marion with a population of 17,803. Other cities include, Herrin population 12,625, Crestwood population 10,604, Carterville population 5,834 and Johnston City population 3,389. See all Williamson County cities & populated places.
Williamson County Populated Places (more)
Cities, towns, neighborhoods & other populated places in Williamson County.
| City Name | Population | Title |
|---|---|---|
| Marion | 17,803 | City in and the county seat of Williamson County, Illinois, United States |
| Herrin | 12,625 | City in Williamson County, Illinois, United States |
| Crestwood | 10,604 | Village in United States of America |
| Carterville | 5,834 | City in Williamson County, Illinois, United States |
| Johnston City | 3,389 | City in Illinois, United States |
| Sleepy Hollow | 3,215 | Village in Illinois |
| Cambria | 1,648 | Village in the United States |
| Crainville | 1,419 | City in Illinois, United States of America |
| Energy | 1,086 | Village in Illinois |
| Hurst | 780 | City in Illinois, USA |
| Bainbridge | 569 | Township in Schuyler County, Illinois |
| Creal Springs | 521 | Township in Williamson County, Illinois |
| Freeman Spur | 276 | Human settlement in United States of America |
| Bush | 263 | Human settlement in Illinois, United States of America |
| Colp | 208 | Human settlement in Illinois, United States of America |
| Spillertown | 197 | Human settlement in Illinois, United States of America |
Weather
A chance of showers and thunderstorms before 7am, then a chance of showers and thunderstorms between 7am and 1pm, then showers and thunderstorms likel...
7-Day ForecastOfficial website of Williamson County
Official Website- Marion
Demographics
The population of Williamson County increased by 0.09% in 10 years.
| Year | Population | % Change | Method |
|---|---|---|---|
| 2010 | 66,357 | - | census |
| 2011 | 66,732 | 0.56% | estimation process |
| 2012 | 66,776 | 0.07% | estimation process |
| 2013 | 67,450 | 1% | estimation process |
| 2014 | 67,412 | -0.06% | estimation process |
| 2015 | 67,428 | 0.02% | estimation process |
| 2016 | 67,454 | 0.04% | estimation process |
| 2017 | 67,049 | -0.6% | estimation process |
| 2018 | 66,982 | -0.1% | estimation process |
| 2019 | 66,597 | -0.58% | estimation process |
| 2020 | 66,415 | -0.27% | estimation process |
Other places with the same name (2)
- Williamson County, Texas county in Tennessee, United States with a population of 617,855 people.
- Williamson County, Tennessee county in Tennessee, United States with a population of 245,348 people.
Illinois Other Counties (more counties)
| County Name | Population | Title |
|---|---|---|
| Cook County | 5,108,284 | County in Illinois, United States |
| Chicago | 2,677,643 | The third most populous city in the United States and the center of the Chicago metropolitan area. |
| DuPage County | 917,481 | County in Illinois, United States |
| Lake County | 693,593 | County in Oregon, United States |
| Will County | 688,726 | County in Illinois, United States |
| Kane County | 531,010 | County in southern Utah, United States |
| McHenry County | 305,888 | County in Illinois, United States |
| Winnebago County | 281,295 | County in Illinois, United States |
| Madison County | 262,635 | County in Montana, United States |
| Saint Clair County | 258,046 | The County of St. |
| Champaign County | 209,192 | County in Illinois, United States |
| Aurora | 196,383 | The second most populous city in Illinois. |
| Sangamon County | 193,882 | County in Illinois, United States |
| Peoria County | 177,652 | County in Illinois, United States of America |
| McLean County | 171,256 | County in North Dakota, United States |
| Naperville | 147,986 | The second most populous city in Illinois. |