Area codes 847 and 224 are telephone area codes in the North American Numbering Plan (NANP) for the U.S. state of Illinois. The numbering plan area (NPA) comprises the northeastern part of Illinois and many northern suburbs of Chicago. This includes most of Lake County, the northern part of Cook County, the northern part of Kane County, and a small part of McHenry County.
Area code 847 was created on January 20, 1996, in a three-way split of area code 708. Area code 847 was involved in the first trial of telephone number pooling in the United States in June 1998, to avert central office code exhaustion in the numbering plan area.[1] Nevertheless, within only five years, 847 was already close to exhaustion from the rapid growth in telecommunication services in the Chicago suburbs and the proliferation of cell phones and pagers. On January 5, 2002, area code 224 was assigned to overlay area code 847. This required ten-digit dialing in all affected communities.