I had a devil of a time finding simple GeoJSON and KML boundary files for US counties and states. Eventually I realized that I could get shapefiles from the United States Census Cartographic Boundary Files and convert them to GeoJSON and KML formats using the MyGeoData vector converter.
The result is the following set of boundary files. Since copyright protection is not available for any work of the United States Government, you should all be free to use for any purpose. The Census Bureau does request to be cited as a source.
These files are available in various resolutions and are all derived from the 2010 census. The 500k files are the most detailed, but also the largest. The 20m files are the smallest, but at the cost of some dramatic simplification. The 5m files fall somewhere between the other two.
|US Outline||SHP, KML, GeoJSON||SHP, KML, GeoJSON||SHP, KML, GeoJSON|
|US States||SHP, KML, GeoJSON||SHP, KML, GeoJSON||SHP, KML, GeoJSON|
|US Counties||SHP, KML, GeoJSON||SHP, KML, GeoJSON||SHP, KML, GeoJSON|
|US Congressional (see note)|| ||SHP, KML, GeoJSON||SHP, KML, GeoJSON|
Note, I received the following note from Peter T in February 2016:
I had to do a little housekeeping before JSON.parse() would correctly parse the data Iím using (with up-to-date Safari), even though the file passed a JSON validator. I want to pass on what I did. Iím using only data for the state of Georgia from the 20m file. I did two things:
1. removed new-line characters, \n, between each of the counties, and
2. removed several (around twenty) extra sets of square brackets, [ ], within the county coordinates vectors.
JSON.parse() now seems to work fine on the Georgia numbers. The attached (Clean Georgia.txt) txt file is the cleaned version that I am using.
Note, I received the following observation from a user in November 2013, so stay alert. I make no promises about the accuracy of these files, I just used the conversion tools listed above.
Was using these, gratefully, but just noticed that California districts are not accurate for 113th Congress. For instance, in gz_2010_us_500_11_20m.json look in the northern part of the state. Not sure of accuracy other states. Ė MR
I believe the issue is that congressional redistricting from the census is not fully reflected in the 2010 files. If you are depending on congressional boundaries, be warned!
If the files you need are not here, don't be afraid of going to the source and converting them yourself!