Boundary Atlas

How to make a map of your data by county, city or district

Get the boundaries as GeoJSON, join your numbers on the area code, and colour by value. One get_boundaries call returns every county, city, ZIP, district or precinct inside a state or county, at a detail level that fits a web map.

Who this is for

Ask your agent

With Boundary Atlas added to Claude, ChatGPT, Cursor or Codex (free, no key; how):

Using Boundary Atlas, get Ohio's counties as GeoJSON at low detail and make a choropleth of this CSV by county FIPS.

Step by step

  1. Pick the level. county, place (city), zcta, congressional_district, state_senate_district, state_house_district or precinct.
  2. Get the shapes. get_boundaries(id="us:state:<FIPS>", children_level="county", detail="low"). Large sets come back as a download link that works for an hour.
  3. Join and colour. Join on code (FIPS for counties) and colour by value in MapLibre, Leaflet, Datawrapper, Flourish or QGIS.
  4. Trim water. clip_to_land (on by default) trims open water so coastal shapes look right.

Live example

Ohio's 88 counties in one call, light enough for a web map:

get_boundaries(id="us:state:39", children_level="county", detail="low")

Features carry id, code (the county FIPS) and name: join your data on code, then colour by value in MapLibre, Leaflet, Datawrapper, Flourish or QGIS.

Things to know

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