Chris Mueller – Visualmotive

Thoughts on maps and visualization

Mapping US Counties with Cartographer.js

Map of California County Populations produced with Cartographer.js

Map of California County Populations produced with Cartographer.js

The most recent release of Cartographer.js supports county-level choropleth maps. This was the number one requested feature for Cartographer and I am delighted to finally be able to offer it in an official package. Many thanks to Ben Cohen and Xanthippe Wedel for making this a reality. The image above is a snapshot of the California county populations map.

Counties are drawn using the same efficient polygon encoding as states, and they can be easily referenced by name. All color schemes and other choropleth map features work for counties just as they worked for states. Click here to download Cartographer.js v0.4 with full county support.

Some additional notes about this release:

  • Loading all US counties into a Google Maps is quite a challenge, and it’s recommended that you only use Cartographer’s county mapping facility for a few states at a time unless you wish to stall out older browsers. Google Chrome handles the large datasets gracefully, if slowly.
  • Adding counties increases the filesize of Cartographer.js significantly. If you don’t need counties, feel free to use an older version for now, and this should be fixed in an upcoming release.


May 4, 2010

Category: Maps

Tagged: ,


  1. Paco says:

    Hi Chris,

    it would be very nice to have a tutorial or something on how to encode the plylines and create the js files with the polygons. that way we could collaborate to improve cartographerjs for many more countries in the world :)!

  2. Paco, thanks for the idea. The Polyline encoding is outlined in depth at

    I will also to write something more comprehensive outlining this process.

  3. Paco says:

    Thanks Chris, I will study it. I will try to map spain provinces in the library.

  4. David Wallace says:

    Is there any plans to migrate Cartographerjs to work with Google Maps V3?