Some of the cities, towns, and places in Clinton County are Albers, Aviston, Bartelso, Beckemeyer, Boulder, Breese, Brookside, Carlyle, Centralia, Clement, Damiansville, Ferrin, Germantown, Harbor Light Bay, Hoffman, Huey, Irishtown, Jamestown, Keyesport, Lake, Looking Glass, Marydale, Meridian, New Baden, New Memphis, New Memphis Station, North Harbor, Panorama Hills, Posey, Royal Lake Resort, Saint Rose, Santa Fe, Shattuc, Snearlyille, Stottletown, Sugar Creek, Trenton, Wade, Wamac, Wertenberg, Wheatfield
Clinton County is located in the U.S. state of Illinois. At the 2020 census, the population was 36,899. Its county seat is Carlyle.In 1960, the United States Census Bureau placed the mean center of U.S. population in Clinton County.Clinton County is part of the St. Louis, MO-IL Metropolitan Statistical Area.