Area Code 815 History:
Area code 815 was put into service. In 1957 area code 815 was split, along with a portion of area code 217, to form area code 309. In 2007 area code 815 was overlaid with area code 779.
Counties in Illinois within area code 815 include:
Boone County, Bureau County, Carroll County, DeKalb County, Ford County, Grundy County, Henry County, Iroquois County, Jo Daviess County, Kane County, Kankakee County, Kendall County, La Salle County, Lee County, Livingston County, Marshall County, McHenry County, McLean County, Ogle County, Putnam County, Stephenson County, Whiteside County, Will County, and Winnebago County.
Major cities or places in Illinois within area code 815 include:
Area codes 779 and 815 serve a large area of northern Illiois including the larger cities and communities of Crystal Lake, DeKalb, Freeport, Joliet, Kankakee, Loves Park, Machesney Park, McHenry, Rockford, Romeoville and Woodstock, in addition to many smaller communities within the area codes 779 and 815 overlay service area.