Area coe 815 is a telephone area code for most of the northern third of the state of Illinois, less the core of the Chicago metropolitan area and the area around Moline. It was one of the four original Illinois area codes set up in 1947. A new overlay area code 779 was implemented on March 17, 2007. No old telephone numbers were reassigned to this area code; rather, it became available for new telephone prefixes on that date. A month earlier, on February 17, 11-digit dialing was implemented for area code 815 in preparation for the 779 overlay.