Note that this list refers only to the population of individual municipalities within their defined limits, which does not include other municipalities or unincorporated suburban areas within urban agglomerations. A different ranking is evident when considering metropolitan area populations.
| Rank |
City |
County |
Population
(2008 est.)[1] |
Population
(2000 Census)[1] |
Change
(%) |
| 1 |
Chicago |
Cook, DuPage |
&0000000002853114.0000002,853,114 |
&0000000002896016.0000002,896,016 |
-1.5% |
| 2 |
Aurora |
Kane, DuPage, Kendall, Will |
&0000000000171782.000000171,782 |
&0000000000142990.000000142,990 |
20.1% |
| 3 |
Rockford |
Winnebago |
&0000000000157272.000000157,272 |
&0000000000150115.000000150,115 |
4.8% |
| 4 |
Joliet |
Will, Kendall |
&0000000000146125.000000146,125 |
&0000000000106221.000000106,221 |
37.6% |
| 5 |
Naperville |
DuPage, Will |
&0000000000143117.000000143,117 |
&0000000000128358.000000128,358 |
11.5% |
| 6 |
Springfield |
Sangamon |
&0000000000117352.000000117,352 |
&0000000000111454.000000111,454 |
5.3% |
| 7 |
Peoria |
Peoria |
&0000000000114114.000000114,114 |
&0000000000112936.000000112,936 |
1% |
| 8 |
Elgin |
Kane |
&0000000000106330.000000106,330 |
&0000000000094487.00000094,487 |
12.5% |