| | Description: | Mason County, located in central Illinois, covers an area of 539 square miles and had a 2003 population of 15,884, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Mason County was the 48th largest county in Illinois geographically, but 29th smallest in terms of population. Combining these two measures, Mason County had the 18th lowest population density per square mile among Illinois 102 counties. | |
