The state of Illinois, USA is currently served by a total of 17 area codes:
These Illinois area codes overlay (cover the same geographic area). The first code listed is the parent code. Overlay area codes are added when no more phone numbers are available in an existing Numbering Plan Area.
| City | County | Area Codes |
|---|---|---|
| Addison | Dupage | 630, 331 |
| Algonquin | McHenry | 847, 224 |
| Arlington Heights | Cook | 847, 224 |
| Aurora | Kane | 630, 331 |
| Bartlett | Dupage | 630, 331 |
| Belleville | St Clair | 618, 730 |
| Berwyn | Cook | 708, 464 |
| Bloomington | McLean | 309, 861 |
| Bolingbrook | Will | 630, 331 |
| Buffalo Grove | Lake | 847, 224 |
| Calumet City | Cook | 708, 464 |
| Carol Stream | Dupage | 630, 331 |
| Carpentersville | Kane | 847, 224 |
| Champaign | Champaign | 217, 447 |
| Chicago | Cook | 773, 872 |
| Chicago (downtown area) | Cook | 312, 872 |
| Cicero | Cook | 708, 464 |
| Crystal Lake | McHenry | 815, 779 |
| Danville | Vermilion | 217, 447 |
| Decatur | Macon | 217, 447 |
| Dekalb | Dekalb | 815, 779 |
| Des Plaines | Cook | 847, 224 |
| Downers Grove | Dupage | 630, 331 |
| Elgin | Kane | 847, 224 |
| Elk Grove Village | Cook | 847, 224 |
| Elmhurst | Dupage | 630, 331 |
| Evanston | Cook | 847, 224 |
| Galesburg | Knox | 309, 861 |
| Glendale Heights | Dupage | 630, 331 |
| Glenview | Cook | 847, 224 |
| Gurnee | Lake | 847, 224 |
| Hanover Park | Cook | 630, 331 |
| Hoffman Estates | Cook | 847, 224 |
| Joliet | Will | 815, 779 |
| Lombard | Dupage | 630, 331 |
| Moline | Rock Island | 309, 861 |
| Mount Prospect | Cook | 847, 224 |
| Mundelein | Lake | 847, 224 |
| Naperville | Will | 630, 331 |
| Normal | McLean | 309, 861 |
| Northbrook | Cook | 847, 224 |
| Oak Lawn | Cook | 708, 464 |
| Oak Park | Cook | 708, 464 |
| Orland Park | Cook | 708, 464 |
| Oswego | Kendall | 630, 331 |
| Palatine | Cook | 847, 224 |
| Park Ridge | Cook | 847, 224 |
| Pekin | Tazewell | 309, 861 |
| Peoria | Peoria | 309, 861 |
| Plainfield | Will | 815, 779 |
| Quincy | Adams | 217, 447 |
| Rock Island | Rock Island | 309, 861 |
| Rockford | Winnebago | 815, 779 |
| Romeoville | Will | 815, 779 |
| Schaumburg | Cook | 847, 224 |
| Skokie | Cook | 847, 224 |
| Springfield | Sangamon | 217, 447 |
| St Charles | Kane | 630, 331 |
| Streamwood | Cook | 630, 331 |
| Tinley Park | Cook | 708, 464 |
| Urbana | Champaign | 217, 447 |
| Waukegan | Lake | 847, 224 |
| Wheaton | Dupage | 630, 331 |
| Wheeling | Cook | 847, 224 |
| Woodridge | Dupage | 630, 331 |