| Description: | Boone County, located in northern Illinois, covers an area of 514 square miles and had a 2003 population of 46,477, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Boone County was the 10th smallest county in Illinois geographically, but 32nd largest in terms of population. Combining these two measures, Boone County had the 17th highest population density per square mile among Illinois 102 counties. | |