County Value Atlas

A modern rebuild of the 2017 EPFL real-estate map. The app visualizes Zillow's smoothed, seasonally adjusted upper-tier ZHVI for U.S. counties in an interactive WebGL map.

Requires Node.js 22.12 or newer.

npm install
npm run dev

Create a production build with npm run build and preview it with npm run preview.

The included GitHub Actions workflow builds and publishes the site on every push to main. vite.config.js automatically uses the repository name as Vite's base path, so project Pages URLs such as https://USERNAME.github.io/county-value-atlas/ resolve bundled assets correctly.

npm run update:data

The updater downloads the current County_zhvi_uc_sfrcondo_tier_0.67_1.0_sm_sa_month.csv release from Zillow Research, validates its schema, and replaces the bundled CSV. Zillow says its housing CSVs are updated monthly and that download paths can occasionally change; if the command reports an HTTP error, confirm the current county download from Zillow Research data.

• Vite 8
• deck.gl 9.4
• D3 7.9
• TopoJSON Client 3.1

The original legacy assets remain in place for historical reference but are no longer loaded by the application.