Saint Clair County, Illinois
Saint Clair County: The County of St.
About
Saint Clair County is a county located in the U.S. state of Illinois. As of the 2010 census, the population was 270,056 and a population density of 155 people per km². After 10 years in 2020 county had an estimated population of 258,046 inhabitants. Its county seat is Belleville. The county was created 235 years ago in 1790.
County Snapshot
Saint Clair County at a glance
Saint Clair County currently has 35 quality-checked populated place pages linked on MapSof, making it easier to jump from the county overview into local city pages.
Mapped populated places
35
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
BellevillePopulation 40,536
Top linked places
Quick Facts about Saint Clair County
| Population | 258,046 (2020) |
| Country | United States of America |
| State | Illinois (United States) |
| Different from | St. Clair County, St. Clair County, St. Clair County |
| Area | 1746 km2 |
| Water as percent of area | 2.4% |
| Land as percent of area | 97.6% |
| Latitude & Longitude | 38.4703,-89.9284 |
| Named for | Arthur St. Clair |
| Capital | Belleville |
| Establishment | April 27, 1790 |
| Time Zone | America/Chicago |
| Local time | 09:13:47 (19th April 2026) |
| Density | 148 Pop. per km² as of 2020 |
| Population growth | -4.65% (2010-2020) |
| Weather | 66℉ Sunny 7-days weather |
Geography
Saint Clair County is located at 38°28'13"N 89°55'42"W (38.4703100, -89.9284100). It has 2 neighbors: Monroe County and Randolph County.
Saint Clair County map
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The largest city of Saint Clair County is Belleville with a population of 40,536. Other cities include, East Saint Louis population 25,776, Crest Hill population 20,209, Fairview Heights population 16,127 and Cahokia population 13,742. See all Saint Clair County cities & populated places.
Saint Clair County Populated Places (more)
Cities, towns, neighborhoods & other populated places in Saint Clair County.
| City Name | Population | Title |
|---|---|---|
| Belleville | 40,536 | The county seat of St. |
| O'Fallon | 29,606 | Township in St. |
| East Saint Louis | 25,776 | City in St. |
| Crest Hill | 20,209 | City in Will County, Illinois |
| Fairview Heights | 16,127 | City in Saint Clair County, Illinois, United States |
| Cahokia | 13,742 | Village in St. |
| Shiloh | 13,653 | Town in St. |
| Swansea | 13,276 | Village in St. |
| Pontiac | 11,176 | City in Illinois, USA |
| Summit | 10,977 | Village in Illinois, USA |
| Mascoutah | 8,076 | City in Saint Clair County, Illinois, United States |
| Centreville | 4,844 | City in Illinois, United States |
| Lebanon | 4,225 | City in St. |
| Freeburg | 4,223 | City in Illinois, United States of America |
| Rosemont | 4,147 | Village in the U. |
| Caseyville | 4,115 | City in Illinois, United States of America |
Official website of Saint Clair County
Official WebsiteDemographics
According to census records, the population of Saint Clair County decreased by 4.65% in 10 years.
| Year | Population | % Change | Method |
|---|---|---|---|
| 2010 | 270,056 | - | census |
| 2011 | 270,048 | -0% | estimation process |
| 2012 | 268,673 | -0.51% | estimation process |
| 2013 | 266,831 | -0.69% | estimation process |
| 2014 | 265,941 | -0.33% | estimation process |
| 2015 | 264,858 | -0.41% | estimation process |
| 2016 | 263,187 | -0.63% | estimation process |
| 2017 | 262,600 | -0.22% | estimation process |
| 2018 | 261,360 | -0.47% | estimation process |
| 2019 | 259,686 | -0.64% | estimation process |
| 2020 | 258,046 | -0.64% | estimation process |
People born in Saint Clair County (4)
People born in Saint Clair County, including baseball player Neal Cotts, artist Paul Soldner, politician Charles A. Karch, .
More notable people
- Alfred W. Woods (American architect) he was born in 30/01/1857
Other places with the same name (3)
- Saint Clair County, Michigan county in Alabama, United States with a population of 159,293 people.
- Saint Clair County, Alabama county in Alabama, United States with a population of 90,739 people.
- Saint Clair County, Missouri county in Missouri, United States with a population of 9,689 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 |
| 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. |
| Rockford | 144,835 | The second most populous city in Illinois. |