| Description: | Shelby County, located in central Illinois, covers an area of 758 square miles and had a 2003 population of 22,407, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Shelby County was the 18th largest county in Illinois geographically, but 55th largest in terms of population. Combining these two measures, Shelby County had the 19th lowest population density per square mile among Illinois 102 counties. | |