| | Description: | Rock Island County, located in northwestern Illinois, covers an area of 427 square miles and had a 2003 population of 147,912, according to estimates by the U.S. Department of Commerce's Bureau of the Census. Using these figures, Rock Island County was the 67th largest county in Illinois geographically, but 14th largest in terms of population. Combining these two measures, Rock Island County had the 10th highest population density per square mile among Illinois 102 counties. | |
