> ## Documentation Index
> Fetch the complete documentation index at: https://docs.boundaries.io/llms.txt
> Use this file to discover all available pages before exploring further.

# List census block GEOIDs for a county

> Returns the list of census block GEOIDs in the given county and state (no geometry).



## OpenAPI

````yaml /openapi-us.json get /rest/v1/public/boundary/censusblock/county/{county}/state/{state}/geoid
openapi: 3.1.0
info:
  title: Boundaries.io – United States
  version: v1
servers:
  - url: https://api.boundaries.io/unitedstates
security:
  - bearer: []
tags:
  - name: States & Territories
    description: >-
      State and territory boundaries by USPS abbreviation, including territories
      such as PR, GU, VI, AS and MP.
  - name: Neighborhoods
    description: >-
      Neighborhood boundaries by name, city, county or state, point-in-polygon
      lookup, and neighborhood-name listings.
  - name: Boundaries (v1)
    description: >-
      General boundary search by ZIP code, city, county or state, and by
      bounding box, FIPS code, point, or radius. v1 is kept for backward
      compatibility; new integrations should use v2.
  - name: H3 Utilities
    description: >-
      Uber H3 hexagonal-index helpers: hexagon polygons for an index, distance
      between two indexes, index lookup for a lat/lon at a given resolution, and
      hex/long index conversion.
  - name: Census Blocks
    description: >-
      U.S. Census block boundaries by GEOID, county and state, or location, plus
      GEOID and county-name listings.
  - name: Country
    description: United States national boundary.
  - name: Addresses
    description: >-
      Boundary lookup for a street address (street number, street name, ZIP
      code).
  - name: Cities
    description: City boundary lookup by city and state name.
  - name: States
    description: State boundaries by name and point-in-polygon state lookup.
  - name: Carrier Routes
    description: USPS carrier route boundaries by ZIP code or carrier route ID.
  - name: Census Tracts
    description: >-
      U.S. Census tract boundaries by GEOID, tract code, county and state, or
      location, plus GEOID and county-name listings.
  - name: Counties
    description: >-
      County boundaries by name and state, by list, or by location, plus
      county-name listings per state.
  - name: Places
    description: >-
      Census-designated place boundaries (cities, towns, CDPs) by name and state
      or by location, plus place-name listings per state.
  - name: ZIP Codes (v1)
    description: >-
      ZIP code (ZCTA) boundaries by ZIP, city, county or state, bounding box,
      radius, point, FIPS code, or WKT geometry. v1 is kept for backward
      compatibility; new integrations should use v2.
  - name: ZIP Code H3
    description: >-
      H3 hexagon coverage of ZIP code boundaries: hexagon by index, hexagon or
      index at a location, and distance between two indexes.
paths:
  /rest/v1/public/boundary/censusblock/county/{county}/state/{state}/geoid:
    get:
      tags:
        - Census Blocks
      summary: List census block GEOIDs for a county
      description: >-
        Returns the list of census block GEOIDs in the given county and state
        (no geometry).
      operationId: findGeoidsByCounty_1
      parameters:
        - name: county
          in: path
          required: true
          schema:
            type: string
        - name: state
          in: path
          required: true
          schema:
            type: string
      responses:
        '200':
          description: GeoJSON FeatureCollection, or a JSON array for name/ID listings
          content:
            '*/*':
              schema:
                type: string
        '400':
          description: Missing or invalid parameter
          content:
            '*/*':
              schema:
                type: string
        '401':
          description: Missing, invalid or inactive API key
          content:
            '*/*':
              schema:
                type: string
components:
  securitySchemes:
    bearer:
      type: http
      scheme: bearer

````

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