Area Code 312-929 located in CHICAGO, COOK, IL, more detail is as below. Place NPA (Numbering Plan Area) : 312 NXX (Local Number Prefix) : 929 City : CHICAGO County : COOK State : IL (Illinois) NXX Use Type : Landline NXX Intro Version : 4/27/2006 FIPS (Federal Information Processing Standards) : 17031 LATA (Local Access Transport Area) : 358 Rate Center : CHICGOZN01 ZIP Code Count : 0 ZIP Code Frequency : Most frequently occurring ZIP Code, although percentage is unknown. ZIP Code : 60606 Other Information NPANXX : 312929 County Population : 0 Switch CLLI (Common Language Location Identifier) : CHCGILNEDSZ 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 : T-MOBILE USA, INC. OCN (Operating Company Number) : 6529 Coverage Area Name : CHICAGO Latitude : 41.8839 Longitude : -87.6369 ‹ previous : 312-928 next › : 312-930 Telephone Number List 312-929-0000 ~ 312-929-9999