Area codes 815 and 779

When the American Telephone and Telegraph Company (AT&T) created the first nationwide telephone numbering plan for Operator Toll Dialing in 1947, the state of Illinois was divided into four numbering plan areas (NPAs), generally laid out as a southern, central, and northern area, and a region around and including the city of Chicago. The northern NPA was assigned area code 815 in the group of 86 original North American area codes.

After September 1956,[1] the 815 numbering plan area was divided roughly in half along a north-westerly to south-easterly running line, assigning area code 309 to its western part, including the Illinois side of the Quad Cities. The new area code was one of the first area codes not serving an entire state, but having the digit 0 in the middle position of the code. It was the only new area code created in Illinois between 1947 and the 1989 creation of area code 708. When forming 309 the area was combined with part of the northern portion of area code 217.[2]

In preparation of an overlay plan with the new area code 779, all calls from the 815 area needed to be dialed with an area code beginning on February 17, 2009. A month later, area code 779 was activated.

• List of North American Numbering Plan area codes
• List of Illinois area codes

• NANPA area code map of Illinois
• Area Code Overlay Approved for 815 Area Code - general information from AT&T, the RBOC for the area code

40.195659°N 89.516602°W / 40.195659; -89.516602