| District of Illinois area codes: 815 | |
|---|---|
| Country | United States |
| State/Province | Illinois |
| Major City | Chicago |
| Time Zone | Central |
| Prefix | County | Primary City | Company |
|---|---|---|---|
| 815-281 | Jo Daviess | Galena, IL | United States Cellular Corp. - Illinois |
| 815-282 | Winnebago | Loves Park, IL | Ameritech Illinois |
| 815-283 | Dekalb | Dekalb, IL | Mediacom Telephony Of Illinois |
| 815-284 | Lee | Dixon, IL | Gallatin River Communications DBA Centurylink |
| 815-285 | Lee | Dixon, IL | Gallatin River Communications DBA Centurylink |
| 815-286 | Dekalb | Hinckley, IL | Frontier North |
| 815-287 | Grundy | Verona, IL | Ameritech Illinois |
| 815-288 | Lee | Dixon, IL | Gallatin River Communications DBA Centurylink |
| 815-289 | Winnebago | Rockford, IL | United States Cellular Corp. - Illinois |
| 815-290 | Grundy | Minooka, IL | Sbc Internet Services |
| 815-291 | Stephenson | Freeport, IL | United States Cellular Corp. - Illinois |
| 815-292 | Winnebago | South Beloit, IL | Bergen Telephone Co. - Illinois |
| 815-293 | Will | Romeoville, IL | Ameritech Illinois |
| 815-294 | Cook | La Grange Park, IL | Usa Mobility Wireless |
| 815-295 | Kankakee | Kankakee, IL | T-mobile Usa |
| 815-296 | Winnebago | Rockford, IL | Usa Mobility Wireless |
| 815-297 | Stephenson | Freeport, IL | Frontier North |
| 815-298 | Winnebago | Rockford, IL | Cellco Partnership DBA Verizon Wireless |
| 815-299 | Winnebago | Rockford, IL | United States Cellular Corp. - Illinois |
| 815-300 | Cook | Chicago, IL | Ameritech Illinois |
There are 785 prefixes, In the code area, the major cities are Belvidere, IL;Crystal Lake, IL;De Kalb, IL;Freepor. The major city is Chicago.