| | Description: | Marion County, located in southern Illinois, covers an area of 572 square miles and had a 2003 population of 40,751, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Marion County was the 40th largest county in Illinois geographically, but 33rd largest in terms of population. Combining these two measures, Marion County had the 35th highest population density per square mile among Illinois 102 counties. | |
