A list of every FIPS code (Census Code) and its corresponding GNIS ID. This is nothing but a long CSV file, listing only the IDs. This includes every FIPS code—not every GNIS ID—and is derived from NationalFedCodes_20140601.zip at the U.S. Board of Geographic Names' website. It's simply that file, with all data stripped out other than our two fields.

This data is available via an API, in the format https://fipsgnis.com/FIPSCODE.json, e.g. a query for for New York, New York, to https://fipsgnis.com/410494.json, returns the following:

{
  "fips": "410494",
  "gnis": "36061"
}

The API consists of static files hosted on S3, provided via CloudFront, so there's no need to be gentle—query all you need, at whatever rate you need. But if you prefer something local and faster, you can generate your own copy.

It's not yet possible to query by GNIS ID, only by FIPS code. But that's planned.

You can generate your own, more up-to-date version of this.

1. Clone or download this repository.
2. Edit the included run.sh script to remove everything after csv.sh.
3. Run run.sh (./run.sh).

Make your own API.

1. Clone or download this repository.
2. Have awscli installed and configured on your system (to write files to S3). Alternately, edit run.sh to erase everything after api.sh and upload the resulting files wherever you care to host your API.
3. Run run.sh (./run.sh).