The 815 area code serves northern Illinois except for the Chicago metro area. The 815 area code has been in service since January 01, 1947.
Illinois Counties within Area Code 815:
Boone, Bureau, Carroll, DeKalb, Ford, Grundy, Henry, Iroquois, Jo Daviess, Kane, Kankakee, Kendall, La Salle, Lee, Livingston, Marshall, McHenry, McLean, Ogle, Putnam, Stephenson, Whiteside Count, Will , and Winnebago.
Illinois Major Cities within Area Code 815:
Rockford, Joliet, DeKalb, Crystal Lake, Romeoville, Plainfield, Kankakee, McHenry, Freeport, Belvidere, Woodstock, New Lenox, Loves Park, Machesney Park, Lockport, Crest Hill, Ottawa, Bourbonnais, Sycamore, Frankfort, Bradley, Dixon, Shorewood, Sterling, Streator, Morris, Channahon, Pontiac, Minooka, Roscoe, Peru, LaSalle, Rochelle, Harvard, Frankfort Square, Rock Falls, Manteno, South Beloit, Rockton, Princeton, Marengo, Mendota, Manhattan, Bolingbrook, Johnsburg, Braidwood, Sandwich, Lakemoor, Wilmington, Spring Grove.
Area Code 815 Time Zone?
Central time zone is also known as America/Chicago.
Go here to see the complete list of United States Area Codes.