Highway guides · Mile marker data

Where can I download milepost GIS data?

Your state DOT's GIS portal is the place to start. Most publish milepost or reference post points on ArcGIS, and you can export them as GeoJSON or a shapefile. For all 50 states in one layout, download the free Utah sample of the MileCheck dataset.

From a state ArcGIS layer

Find the milepost layer on the state's open data site. Its REST query URL can return GeoJSON:

…/FeatureServer/0/query?where=1%3D1&outFields=*&outSR=4326&f=geojson

Large layers page at 1,000 or 2,000 records, so request in batches with resultOffset.

What you'll have to clean

Route names in agency codes, such as IR15N or 0095X, instead of I-15 or I-95.
Internal reference numbers mixed in with sign numbers.
Points at every tenth of a mile when you wanted whole miles.
Coordinates in a state plane or Web Mercator projection.

The 50-state file

The MileCheck milepost dataset has those steps done. It has 396,842 marker positions in one schema, as CSV and GeoJSON in WGS84. The Utah sample has 7,487 positions and a README. No form needed.

Mile marker data for all 50 states

396,842 marker positions as CSV and GeoJSON, one layout for every state, with a list of what changed in each release. Download the Utah sample with no form.

See the dataset The API

Questions, answered

Is there a shapefile?

The MileCheck files are CSV and GeoJSON. Most GIS tools convert GeoJSON to a shapefile in one step.

Can I use state DOT data commercially?

Each agency sets its own terms. The MileCheck dataset lists each state's source and stated terms in its manifest.