FCC Census Block Conversions API

Base URL

https://geo.fcc.gov/api/census

Authentication

No API key and no registration. The FCC publishes this as a public geographic conversion service.

Rate limit

No published limit. Cache results — census block boundaries change only with the decennial census.

Pricing

Free. US government works are in the public domain.

CORS

Enabled — callable directly from browser JavaScript

Official docs

Read the docs

Every request below was executed against the live API on 21 Aug 2026, and the response shown is the real body it returned — not an illustration.

curl 'https://geo.fcc.gov/api/census/area?lat=40.0150&lon=-105.2705&format=json'

const res = await fetch("https://geo.fcc.gov/api/census/area?lat=40.0150&lon=-105.2705&format=json");
if (!res.ok) throw new Error(`Request failed: ${res.status}`);
const data = await res.json();
console.log(data);

import requests

res = requests.get("https://geo.fcc.gov/api/census/area?lat=40.0150&lon=-105.2705&format=json", timeout=20)
res.raise_for_status()
print(res.json())

{
  "input": {
    "lat": 40.015,
    "lon": -105.2705,
    "censusYear": "2020"
  },
  "results": [
    {
      "block_fips": "080130122061017",
      "bbox": [
        -105.27256,
        40.014588,
        -105.27022,
        40.015414
      ],
      "county_fips": "08013",
      "county_name": "Boulder County",
      "state_fips": "08",
      "state_code": "CO",
      "state_name": "Colorado",
      "block_pop_2020": 83,
      "amt": "AMT010",
      "bea": "BEA141",
      "bta": "BTA110",
      "cma": "CMA019",
      "eag": "EAG005",
      "ivm": "IVM019",
      "mea": "MEA033",
      "mta": "MTA022",
      "pea": "PEA020",
      "rea": "REA005",
      "rpc": "RPC004",
      "vpc": "VPC025"
    }
  ]
}

inputobject

Echo of the coordinates and census year used, useful for confirming the vintage.

results[].block_fipsstring

15-digit block FIPS. Truncate to 2, 5 or 11 digits for state, county or tract.

results[].bboxarray

Bounding box of the block as `[west, south, east, north]`.

results[].county_fips / county_namestring

County identifier and name.

results[].state_fips / state_code / state_namestring

State FIPS, two-letter code and full name.

results[].block_pop_2020integer

Population of the block at the 2020 census. Zero means uninhabited.

results[].bea / bta / cma / mta / pea / reastring

FCC market and service area codes used in spectrum licensing.

• Join an address to census demographic or broadband data
• Derive county and state FIPS codes from coordinates
• Look up FCC market areas for a telecom filing
• Validate that a coordinate falls inside the United States
• Aggregate points to census tracts for choropleth mapping

If FCC Census Block Conversions does not fit, these government & open data apis cover similar ground. Every one was called before publishing, and each links to its own reference page with a working curl command and the response it returned.