Cities in St. Clair County, Illinois by Population (2024)

There are 42 cities in St. Clair County, Illinois.

Note: As defined by the US Census Bureau, a city's official boundaries often extend miles beyond the city itself and may even cross county lines. As such, several thousand US cities officially exist in two or more counties (and therefore appear on multiple counties' lists of cities.)

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City
Rank
State
2024 Population
2020 Census
Annual Change
Density (mi²)
Area (mi²)
Belleville1Illinois40,21242,266-1.26%1,73123.23
O'Fallon2Illinois31,85532,307-0.35%2,01715.79
Granite City3Illinois26,70527,516-0.75%1,40419.02
Collinsville4Illinois23,59624,327-0.77%1,54815.24
East St. Louis5Illinois17,38918,400-1.43%1,24913.93
Fairview Heights6Illinois15,94416,667-1.12%1,39511.43
Shiloh7Illinois14,94414,1121.41%1,35311.05
Swansea8Illinois14,51214,3510.28%2,2416.48
Troy9Illinois11,29510,9500.77%1,9845.69
Waterloo10Illinois11,19011,0050.41%1,3598.23
Columbia11Illinois10,89911,033-0.31%1,03310.55
Mascoutah12Illinois8,9758,7390.66%9319.64
Maryville13Illinois8,3358,2570.23%1,4445.77
Pontoon Beach14Illinois5,7865,858-0.31%5819.97
Lebanon15Illinois4,5354,679-0.79%1,6832.69
Freeburg16Illinois4,4744,582-0.6%6536.85
Caseyville17Illinois4,3484,391-0.25%5987.27
Scott AFB18Illinois4,2013,8452.16%9694.34
Millstadt19Illinois3,9024,065-1.04%1,1133.51
Smithton20Illinois3,8654,003-0.9%8584.50
Dupo21Illinois3,7693,976-1.36%5896.40
New Baden22Illinois3,3453,419-0.56%1,8331.82
Madison23Illinois3,0413,137-0.78%21514.14
Trenton24Illinois2,6282,682-0.53%1,3961.88
Washington Park25Illinois2,4662,573-1.08%9662.55
Fairmont City26Illinois2,1472,255-1.24%3466.21
New Athens27Illinois1,8481,947-1.33%8752.11
Marissa28Illinois1,7261,828-1.48%2397.21
Venice29Illinois1,4461,490-0.76%7821.85
Valmeyer30Illinois1,2061,228-0.5%3523.42
Albers31Illinois1,1111,134-0.54%1,1200.99
Brooklyn32Illinois618649-1.28%7620.81
St. Libory33Illinois603629-1.15%6220.97
Lenzburg34Illinois445467-1.33%3851.16
Hecker35Illinois414428-0.96%1,5510.27
East Carondelet36Illinois370390-1.33%3141.18
Summerfield37Illinois328343-1.21%6390.51
Fayetteville38Illinois283293-1.05%9560.30
Sauget39Illinois130138-1.52%284.59
Floraville40Illinois1430-22.22%1770.08
Paderborn41Illinois0650%00.15
Rentchler42Illinois040%00.31
showing: 42 rows

Note: City markers shown outside the county boundary mean that a part of the city extends into this county, but is primarily located in an adjacent county.

What is the largest city in St. Clair County, Illinois?

Belleville is the largest city in St. Clair County.

What is the smallest city in St. Clair County, Illinois?

Rentchler is the smallest city in St. Clair County.

How many cities are in St. Clair County?

There are 42 cities in St. Clair County, Illinois.

Frequently Asked Questions