Area Codes
| 779 | Illinois (Crystal Lake, Rockford, Joliet, and other outlying suburbs of Chicago; It overlays with 815) | More information at: Area Code 779 Phone Number Blocks
| 779 | Illinois (Crystal Lake, Rockford, Joliet, and other outlying suburbs of Chicago; It overlays with 815) | More information at: Area Code 779 Phone Number Blocks