A rate centre (rate center in US usage) is the local area a North American central office code is assigned to: every code, and every thousands-block pooled inside it, belongs to one rate centre, and calls to its numbers have traditionally been rated as local or long distance from it. NANPA's rate-centre report of 24 September 2026 holds 18,452 pairs of a state and a rate-centre code across the 50 states, the District of Columbia and Puerto Rico, under 12,317 distinct names, because the same name recurs from state to state. In Canada the same part is played by the exchange area in the Canadian administrator's table.
Rate centres change slowly and by order: NANPA publishes a list of rate centres split among several area codes by a state commission's order, and a summary of rate-centre consolidations since 2005 (https://www.nanpa.com/reports/co-code-reports, accessed 27 September 2026).
What Spaw answers
region names the rate centre when the numbering metadata's own description of the number names only a state or a country. NANPA writes the names in capitals with the parts it splits a metro area into for billing, and those parts are dropped: SAN FRANCISCO:CENTRAL DA and LOS ANGELES:DA 06 answer "San Francisco, CA" and "Los Angeles, CA". region_level then says locality, as it does for a description that already names a city with its state; it is read from where the description came from and its shape, not measured. A Canadian exchange area is answered the same way ("Toronto, ON"). For a whole prefix, the block report lists up to three rate centres or exchange areas in places when it can only name the state or province, and the page of every state with more than one area code, linked from the United States phone facts, counts its rate centres and lists its area codes with their overlays.
What it does not mean
A rate centre is where the number was issued, not where the person is. A mobile goes wherever its owner does, a VoIP number can be answered anywhere, and a ported number keeps the rate centre of its code. The codes of an overlay share their rate centres, so the rate centre, not the area code, is the finer place name the tables give.