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Playground demo key · api.reefapi.com
post/geo-postal/v1/us_regions2 credits

United States: ZIP code OR coordinates → state, county + 5-digit county FIPS, place, ZIP centroid, and the CGAZ state/county boundary. Built WITHOUT census.gov (GeoNames ZIP directory carries county FIPS; ANSI state-FIPS is a public-domain constant). For census-grade ZCTA + tract/block GEOIDs use the `us_census` action (TIGER/ZCTA polygons + Census Geocoder, gov-pending/91).

Working example
Parameters

Postal code to resolve. Spaces/dashes are ignored, case-insensitive (e.g. '10115', '75001', 'SW1A1AA').

WGS84 latitude of the point to resolve (decimal degrees). (-90–90)

WGS84 longitude of the point to resolve (decimal degrees). (-180–180)

If true, include the (simplified) boundary polygon as GeoJSON. Default false — geometries are large; lookups never depend on this.

request preview
curl -X POST https://api.reefapi.com/geo-postal/v1/us_regions \
  -H "x-api-key: $REEF_KEY" \
  -H "content-type: application/json" \
  -d '{"postal_code":"10001"}'

Hit Send to run this endpoint live.