When working with maps and JavaScript, if you need to outline or shade states or counties on a map you need a huge list of coordinates that make up that shape. Sometimes it’s a single polygon but sometimes, like in the case of Alaska, it’s a MultiPolygon.

I’ve worked on more maps in the last couple months than I have in the last few years but haven’t ever been able to find all of the counties of the US in geoJSON/JSON format, only in KML or CSV.

This weekend I wrote¬†a¬†parser that takes the CSV’s that hold the data and creates individual files for each state as well as a master file for the whole US.


All US State Boundaries

All US State County Boundaries

US County Boundaries State by State