Add congressional districts to a spreadsheet

Why from the address, not the ZIP

ZIP codes are postal routes, not political boundaries, and thousands of them straddle district lines. Assigning districts by ZIP gets a measurable share of a voter file wrong. Geocoding each address to a point and testing the point against the boundary is the only way to be right near a line.

In the spreadsheet tool

1. Open the spreadsheet geocoder with a free key.
2. Drop the file and confirm the address columns.
3. Tick Congressional district and, if you want them, State legislative districts.
4. Geocode and download. New columns: cd_district and cd_name, plus sld_upper and sld_lower if you ticked the state chambers, next to geo_lat, geo_lng and geo_accuracy_type.

Districts are the vintage in TIGER/Line 2025 for the 119th Congress.

With the API

curl -X POST https://api.geocode.net/v1/geocode/batch -H "X-API-Key: YOUR_KEY" \
  -H "Content-Type: application/json" \
  -d '{"addresses": ["1 Loockerman Plz, Dover, DE", "1600 Pennsylvania Ave NW, Washington DC"], "fields": "cd,stateleg"}'

{ "fields": { "congressional_district": { "congress": 119, "district": "00",
              "name": "Congressional District (at Large)", "geoid": "1000" } } }

Check the accuracy column near boundaries

Filter to rows whose accuracy_type is place, zip, county or state. Those rows were placed at an area centroid, so their district is a guess when the area crosses a line. Fix the address (usually a missing city or a typo in the street) and run those rows again.

Related: the free congressional district lookup for one address at a time.