FIPS County Codes

Looking up the counties for a zip code

What is a FIPS code?

A FIPS county code is a five-digit identifier assigned by the Federal Information Processing Standards to uniquely identify every county (and county equivalent) in the United States. The first two digits represent the state and the remaining three identify the county within that state.

The HealthSherpa ICHRA API uses FIPS codes as the fip_code parameter in the Quoting API and Application Deeplink API. This is required because health insurance plans and premiums are rated at the county level — a zip code alone is not specific enough, since a single zip code can span multiple counties with different available plans.

Looking up FIPS codes by zip code

To resolve a zip code to its FIPS county code(s), call the public CMS Marketplace API:

GET https://marketplace-int.api.healthcare.gov/api/v1/counties/by/zip/{zipcode}

Example:

curl https://marketplace-int.api.healthcare.gov/api/v1/counties/by/zip/42003

Response:

{
  "counties": [
    {
      "zipcode": "42003",
      "name": "McCracken County",
      "fips": "21145",
      "state": "KY"
    },
    {
      "zipcode": "42003",
      "name": "Graves County",
      "fips": "21083",
      "state": "KY"
    }
  ]
}

Handling multiple counties

When a zip code spans more than one county, the response will contain multiple entries. The common pattern is to present a dropdown listing the county names and resolve the selection to its fips value behind the scenes — the employee picks "McCracken County" or "Graves County" without ever seeing a FIPS code. If the response contains only one county, you can skip the prompt and use that value directly.

Pass the resolved fips value as the fip_code parameter in your Quoting API or Application Deeplink API request.

Common Implementation Pattern

1. Resolve ZIP to county list.

2. If one county, auto-select.

3. If multiple, show county-name dropdown.

4. Store selected fips internally as fip_code.