| Description: | Clinton County, located in southwestern Illinois, covers an area of 474 square miles and had a 2003 population of 36,135, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Clinton County was the 58th largest county in Illinois geographically, but 40th largest in terms of population. Combining these two measures, Clinton County had the 32nd highest population density per square mile among Illinois 102 counties. | |