Area Code 815 is one of the area codes assigned to Illinois in 1947. Illinois is East North Central State of United States served by area code 815, 779, 847 and 224 together. The 815 code was running out of available phone numbers rapidly around 2007. To overcome the problem it was overlaid by area code 779 on 17th March 2007.
The Code 815 is serving areas of Northern Illinois. The "East North Central" is one of the geographic partitions of United States composed of five states:
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