| Description: | Cook County, located in northeastern Illinois, covers an area of 946 square miles and had a 2003 population of 5,351,552, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Cook County was the 6th largest county in Illinois geographically, but the largest in terms of population. Combining these two measures, Cook County had the highest population density per square mile among Illinois 102 counties. | |