| Description: | Jersey County, located in southwestern Illinois, covers an area of 369 square miles and had a 2003 population of 22,188, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Jersey County was the 20th smallest county in Illinois geographically, but 56th largest in terms of population. Combining these two measures, Jersey County had the 43rd highest population density per square mile among Illinois 102 counties. | |