Area Code 307-228 located in ROCK SPRINGS, SWEETWATER, WY, more detail is as below. Place NPA (Numbering Plan Area) : 307 NXX (Local Number Prefix) : 228 City : ROCK SPRINGS County : SWEETWATER State : WY (Wyoming) FIPS (Federal Information Processing Standards) : 56037 Rate Center : ROCK SPG ZIP Code Count : 0 ZIP Code Frequency : Most frequently occurring ZIP Code, although percentage is unknown. ZIP Code : 82901 Other Information NPANXX : 307228 County Population : 0 Switch CLLI (Common Language Location Identifier) : CSPRWYDHDS0 MSA CBSA (Core Based Statistical Area) : Rock Springs, WY MSA CBSA Code (Core Based Statistical Area) : 40540 Time Zone : Mountain (GMT -07:00) Observes Daylight Saving Time : Yes Latitude : None Longitude : None ‹ previous : 307-227 next › : 307-229 Telephone Number List 307-228-0000 ~ 307-228-9999