| | Description: | Johnson County, located in southern Illinois, covers an area of 346 square miles and had a 2003 population of 12,951, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Johnson County was the 18th smallest county in Illinois geographically, and but 18th smallest in terms of population. Combining these two measures, Johnson County had the 34th lowest population density per square mile among Illinois 102 counties. | |
