Area code 779 was created in 2007 to overlay area code 815, which covers the northern third of Illinois. 10-digit dialing is mandatory.
- 779-216
- Landline Number
- Frankfort, IL
- 779-220
- Landline Number
- Crystal Lake, IL
- 779-229
- Landline Number
- Spring Valley, IL
- 779-232
- Landline Number
- Wilmington, IL
- 779-235
- Cell Number
- Crescent City, IL
- 779-324
- Landline Number
- Frankfort, IL
- 779-333
- Landline Number
- Frankfort, IL
- 779-429
- Landline Number
- Wilmington, IL
- 779-432
- Landline Number
- Sheffield, IL
- 779-444
- Landline Number
- Wonder Lake, IL
- 779-545
- Landline Number
- Mt Morris, IL
- 779-552
- Landline Number
- Belvidere, IL
- 779-800
- Landline Number
- Crystal Lake, IL
- 779-994
- Landline Number
- Crystal Lake, IL