What is an Area Code? An area code is a section of a telephone number that denotes the broad area that the phone receiving the call is based in. Area codes were first introduced circa 1947 for operator use only. Area codes are three-digit numbers that represent Numbering Plan Areas (NPAs). The area code for a particular city or region is the series of numbers that you have to dial before someone’s number if you are making a phone call to that place from a different area. Area code 312 serves the state of Illinois.
The Table Below Shows the Towns and Cities That Use Area Code 312
| Brookfield Buffalo Grove Chicago Cicero Clarendon Hills | Deerfield Glenview Hinsdale La Grange Park Medinah | Northbrook Prospect Heights Roselle Schaumburg Western Springs Wheeling |