Geocode a US street address to lat/lng plus US Census FIPS codes (state/county/tract/block). Backed by the US Census Bureau Geocoder. Query params: street (required, e.g. '1600 Pennsylvania Ave NW'), city (optional, improves accuracy), state (optional, 2-letter abbrev), zip (optional, 5-digit). Returns match: false with no lat/lng when Census can't find the address; payment is charged per call regardless of match outcome.

Reverse-geocode a lat/lng coordinate to its enclosing US Census block (state/county/tract/block FIPS codes). Query params: lat (required, decimal degrees), lng (required, decimal degrees). US-only coverage.