Founded in 1836, Winnebago County is one of 102 counties in the state of Illinois. Historically, Winnebago County was formed from Jo Daviess County. The city of Rockford is the county seat. With FIPS code of 201, Winnebago County has a population of 283,119 and area of 513 square miles (1,329 km2).
List of all cities in Winnebago County, IL alphabetically
| City/Town | Postal Code | Area Code |
| Beloit, IL | 61080 | 815/779 |
| Cherry Valley, IL | 61016 | 815/779 |
| Durand, IL | 61024 | 815/779 |
| Irene, IL | 61016 | 815/779 |
| Loves Park, IL | 61111 | 815/779 |
| 61115 | 815/779 | |
| 61130 | 815/779 | |
| 61131 | 815/779 | |
| 61132 | 815/779 | |
| Machesney Park, IL | 61103 | 815/779 |
| 61111 | 815/779 | |
| 61115 | 815/779 | |
| Morristown, IL | 61109 | 815/779 |
| New Milford, IL | 61109 | 815/779 |
| Pecatonica, IL | 61063 | 815/779 |
| Rockford, IL | 61101 | 815/779 |
| 61102 | 815/779 | |
| 61103 | 815/779 | |
| 61104 | 815/779 | |
| 61105 | 815/779 | |
| 61106 | 815/779 | |
| 61107 | 815/779 | |
| 61108 | 815/779 | |
| 61109 | 815/779 | |
| 61110 | 815/779 | |
| 61112 | 815/779 | |
| 61114 | 815/779 | |
| 61125 | 815/779 | |
| 61126 | 815/779 | |
| 61072 | 815/779 | |
| Roscoe, IL | 61073 | 815/779 |
| Seward, IL | 61077 | 815/779 |
| Shirland, IL | 61079 | 815/779 |
| South Beloit, IL | 61080 | 815/779 |
| Winnebago, IL | 61088 | 815/779 |