303 area code

1. The NPA is the Numbering Plan Area (area code) and NXX is the central office code.
2. For 'Area served' we list the rate center. In the North American Numbering Plan a rate center is a geographic area used to determine local calling boundaries for billing purposes. Its name is generally a locality, often not the only one served by an NPA-NXX combination.
3. The assignment date. If no date is shown the exchange code was assigned before 2001.

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