Significant events for area code 815
| Date |
Details |
| 1947 | One of the four original area codes for Illinois. It covered all of northern Illinois except for the Chicago metro area. |
| 1957 | Area code 309 was created with 309 covering the southwestern area of 815 and part of northern 217 . |
| March 17, 2009 | Area code 779 was overlaid on 815. |