Area Code 203-637 located in OLD GREENWICH, FAIRFIELD, CT, more detail is as below. Place NPA (Numbering Plan Area) : 203 NXX (Local Number Prefix) : 637 City : OLD GREENWICH County : FAIRFIELD State : CT (Connecticut) NXX Use Type : Landline NXX Intro Version : 1994-02-04 FIPS (Federal Information Processing Standards) : 09001 LATA (Local Access Transport Area) : 920 Rate Center : OLDGRNWICH ZIP Code Count : 1869 ZIP Code Frequency : 48 ZIP Code : 06870 Other Information NPANXX : 203637 County Population : 0 Switch CLLI (Common Language Location Identifier) : OGNWCT00RS1 MSA CBSA (Core Based Statistical Area) : Bridgeport-Stamford-Norwalk, CT MSA CBSA Code (Core Based Statistical Area) : 14860 Time Zone : Eastern (GMT -05:00) Observes Daylight Saving Time : Yes Company : SOUTHERN NEW ENGLAND TELEPHONE CO. OCN (Operating Company Number) : 9147 Coverage Area Name : OLD GREENWICH Latitude : 41.0302 Longitude : -73.5668 ‹ previous : 203-637 next › : 203-638 Telephone Number List 203-637-0000 ~ 203-637-9999