Area Code 301-621 located in COLUMBIA, HOWARD, MD, more detail is as below. Place NPA (Numbering Plan Area) : 301 NXX (Local Number Prefix) : 621 City : COLUMBIA County : HOWARD State : MD (Maryland) NXX Use Type : Landline NXX Intro Version : 1994-02-04 FIPS (Federal Information Processing Standards) : 24027 LATA (Local Access Transport Area) : 238 Rate Center : WSNG238Z14 ZIP Code Count : 55 ZIP Code Frequency : 9 ZIP Code : 21045 Other Information NPANXX : 301621 County Population : 0 Switch CLLI (Common Language Location Identifier) : CLMAMDCBDS0 MSA CBSA (Core Based Statistical Area) : Baltimore-Towson, MD MSA CBSA Code (Core Based Statistical Area) : 12580 Time Zone : Eastern (GMT -05:00) Observes Daylight Saving Time : Yes Company : VERIZON MARYLAND, INC. OCN (Operating Company Number) : 9212 Coverage Area Name : GLENN DALE Latitude : 38.9839 Longitude : -76.8136 ‹ previous : 301-621 next › : 301-621 Telephone Number List 301-621-0000 ~ 301-621-9999