Founded in 1836, Whiteside County is one of 102 counties in the state of Illinois. Historically, Whiteside County was formed from Jo Daviess and Henry County. The city of Morrison is the county seat. With FIPS code of 195, Whiteside County has a population of 55,305 and area of 684 square miles (1,772 km2).
List of all cities in Whiteside County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Albany, IL | 61230 | 309 |
| Brookhaven, IL | 61277 | 815/779 |
| Ceffco, IL | 61230 | 309 |
| Clyde, IL | 61270 | 815/779 |
| Coleta, IL | 61081 | 815/779 |
| Deer Grove, IL | 61243 | 815/779 |
| East Clinton, IL | 61252 | 815/779 |
| East Fulton, IL | 61252 | 815/779 |
| Erie, IL | 61250 | 309 |
| Fenton, IL | 61251 | 309 |
| Fulton, IL | 61252 | 815/779 |
| Galt, IL | 61037 | 815/779 |
| Garden Plain, IL | 61252 | 815/779 |
| Genesee, IL | 61270 | 815/779 |
| Hahnaman, IL | 61283 | 815/779 |
| Leon Corners, IL | 61277 | 815/779 |
| Lyndon, IL | 61261 | 815/779 |
| Malvern, IL | 61270 | 815/779 |
| Morrison, IL | 61270 | 815/779 |
| Portland, IL | 61277 | 815/779 |
| Portland Corners, IL | 61277 | 815/779 |
| Prophetstown, IL | 61277 | 815/779 |
| Rock Falls, IL | 61071 | 815/779 |
| Round Grove, IL | 61270 | 815/779 |
| Sterling, IL | 61081 | 815/779 |
| Tampico, IL | 61283 | 815/779 |
| Thomas, IL | 61283 | 815/779 |
| Union Grove, IL | 61270 | 815/779 |
| Ustick, IL | 61270 | 815/779 |
| Wethersfield, IL | 61277 | 815/779 |
| Yeoward Addition, IL | 61071 | 815/779 |
| Yeowardville, IL | 61071 | 815/779 |