| Description: | Peoria County, located in central Illinois, covers an area of 619 square miles and had a 1998 population of 181,609, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Peoria County was the 32nd largest county in Illinois geographically, but 11th largest in terms of population. Combining these two measures, Peoria County had the 11th highest population density per square mile among Illinois 102 counties. | |