St. Clair County, Illinois Cities (2025)

45 cities

City
Rank
2025 Pop.
2020 Pop.
Change
Density
Area (mi²)
Type
Belleville city139,72242,266-1.25%1,71023.23 City
Belleville239,69942,266-1.28%1,70923.23 City
St. Clair township336,30635,7040.92%1,78320.36 Township
Caseyville township434,18235,477-0.72%98034.89 Township
O'Fallon531,74232,307-0.35%2,01015.79 City
O'Fallon township625,80526,370-0.43%73535.11 Township
Centreville township718,86520,132-1.26%67527.93 Township
East St. Louis township817,15818,400-1.39%1,23213.93 Township
East St. Louis917,13618,400-1.45%1,23113.93 City
Fairview Heights1015,76316,667-1.14%1,37911.43 City
Shiloh1115,15214,1121.39%1,37211.05 Village
Swansea1214,55214,3510.28%2,2476.48 Village
Shiloh Valley township1312,96012,8220.29%40831.77 Township
Mascoutah township1410,1359,4072.92%25939.09 Township
Mascoutah159,0348,7390.66%9379.64 City
Stookey township168,6769,212-1.2%32626.58 Township
Canteen township177,6108,001-1%44817 Township
Sugar Loaf township186,5236,933-1.21%21330.58 Township
Millstadt township196,4006,739-0.96%13746.75 Township
Freeburg township204,8925,072-0.65%14234.34 Township
Lebanon township214,6334,833-0.83%12736.47 Township
Lebanon224,4994,679-0.79%1,6692.69 City
Freeburg234,4474,582-0.6%6496.85 Village
Caseyville244,3374,391-0.25%5967.27 Village
Scott AFB254,1263,8450.83%9514.34 CDP
Smithton township263,9784,160-0.92%12332.29 Township
Millstadt273,8614,065-1.05%1,1013.51 Village
Smithton283,8314,003-0.88%8514.50 Village
Dupo293,7173,976-1.38%5816.40 Village
Prairie Du Long township302,5152,646-1.06%7135.46 Township
New Athens township312,3732,526-1.25%7034 Township
Marissa township322,1192,264-1.26%6234.45 Township
New Athens331,8231,947-1.35%8632.11 Village
Marissa341,7011,828-1.45%2367.21 Village
Fayetteville township351,4431,525-1.23%3442.96 Township
Lenzburg township36901949-0.99%3128.91 Township
Engelmann township37715756-1.11%2429.58 Township
Stites township38613650-1.13%2992.05 Township
Brooklyn39610649-1.29%7520.81 Village
St. Libory40597629-1%6150.97 Village
Lenzburg41440467-1.12%3811.16 Village
East Carondelet42365390-1.35%3101.18 Village
Lovejoy township43355374-1.11%1034.69 Township
Summerfield44324343-1.22%6320.51 Village
Fayetteville45281293-0.71%9490.30 Village

St. Clair County Cities Summary

Largest City

Belleville city is the largest city in St. Clair County, with a population of 39,722.

Smallest City

Fayetteville is the smallest city in St. Clair County.

10 Largest Cities

There are 45 cities in St. Clair County, Illinois.

Location of St. Clair County