Area Code 312-223 located in CHICAGO, COOK, IL, more detail is as below. Place NPA (Numbering Plan Area) : 312 NXX (Local Number Prefix) : 223 City : CHICAGO County : COOK State : IL (Illinois) NXX Use Type : Landline NXX Intro Version : 1997-10-11 FIPS (Federal Information Processing Standards) : 17031 LATA (Local Access Transport Area) : 358 Rate Center : CHICGOZN01 ZIP Code Count : 1 ZIP Code Frequency : 4 ZIP Code : 60604 Other Information NPANXX : 312223 County Population : 0 Switch CLLI (Common Language Location Identifier) : CHCGILFRDS1 MSA CBSA (Core Based Statistical Area) : Chicago-Naperville-Joliet, IL-IN-WI MSA CBSA Code (Core Based Statistical Area) : 16980 Time Zone : Central (GMT -06:00) Observes Daylight Saving Time : Yes Company : AMERITECH ILLINOIS OCN (Operating Company Number) : 9329 Coverage Area Name : CHICAGO Latitude : 41.8839 Longitude : -87.6369 ‹ previous : 312-223 next › : 312-223 Telephone Number List 312-223-0000 ~ 312-223-9999