Boundary JSON

A static API for obtaining simplified GeoJSON describing the boundaries of legislative districts.

If you obtain an Open Civic Data Division ID (e.g. ocd-division/country:us/state:ks/sldl:1 you can convert it to a URL like https://data.openstates.org/boundaries/2018/ocd-division/country:us/state:ks/sldl:1.json.

The URL consists of a few parts:

  • https://data.openstates.org/boundaries/ - base URL
  • 2018 - division issue year, currently only 2018 supported (divisions do not change most years)
  • ocd-division/country:us/state:ks/sldl:1 - Open Civic Data Division ID
  • .json - end URL with .json

File Format

  • division_id - Open Civic Data Division ID, same as URL.
  • year - Issue year for Boundary, same as URL.
  • centroid - GeoJSON Point representing the centroid of this boundary.
  • extent - Coordinates for upper-left & lower-right extent of boundary.
  • shape - Simplified GeoJSON MultiPolygon for display purposes. This data has been simplified (losing some detail to gain speed when drawing/processing) and should be used for display but not intersection/point-in-polygon testing.
  • metadata - Metadata that was provided by issuer, typically a bit of Census data. No particular guarantee is made about what is here.

Obtaining ocd-division IDs

If you’re using Open States data you’ll see ocd-division IDs in a few places:

  • The division_id & boundary_id keys in the Districts endpoint of API v1.
  • the id attribute on DivisionNode which can be accessed via Post.