---
title: "County ACS living-arrangements observations by source year"
method: POST
path: "/api/locus_acs_living_arrangements_series"
tags: ["census", "living-arrangements", "time-series", "read-only", "free", "free"]
---

# County ACS living-arrangements observations by source year

`POST /api/locus_acs_living_arrangements_series`

## Request

- Base URL: `https://api.locus.report`
- URL: `https://api.locus.report/api/locus_acs_living_arrangements_series`
- Auth: none required

Source-year ACS five-year B09021 ages 18–34 counts and margins for all household members and children of householders. Caller-chosen county FIPS; observations and gaps, no affordability inference or place verdict. National. Direct flat-body route for this one free resource; no API key, payment, or catalog wrapper. Return only the cited bounded evidence described here; this route never produces a paid brief or full report.

## Request body

- object
  - `stateFips` string, required: Two-digit state FIPS.
  - `countyFips3` string, required: Three-digit county FIPS.
  - `fromYear` integer, required: First source year, 2021–2024.
  - `toYear` integer, required: Last source year, 2021–2024.

## Response `200`

Free cited evidence response.

- object

## Other responses

- `400`: Invalid request body.
- `429`: Rate limited.

---

[API](https://skmtc.dev/locus/apis/locus-api.md) · [All operations](https://skmtc.dev/locus/apis/locus-api/llms.txt) · [OpenAPI document](https://skmtc.dev/locus/apis/locus-api/revisions/ba7786b74adb?raw)