MileCheckIs there a database of every highway mile marker in the US?
Not from the federal government. Each state DOT publishes its own mile marker layer, in its own format, and some states number their roads differently. MileCheck has combined all 50 states into one table of 396,842 marker positions with one schema.
Why there is no single federal file
Mile markers belong to each state. The federal highway inventory (FHWA's HPMS) describes road lines and their lengths, not where each sign stands. So the marker positions live in 50 separate state datasets, and a data.gov search mostly turns up those state and county layers.
How the state datasets differ
- Format. One state publishes an ArcGIS service, another a shapefile, another a CSV, each with different field names.
- Route names. Some states use the route a driver reads on the sign, like I-84. Others use internal highway numbers. Oregon's layer, for example, names highways by ODOT number and name.
- What a point means. Some states survey every sign. Others place points along the route line at each mile.
- Numbering. California uses postmiles that restart at each county line. New York uses reference markers on state roads. Interstates use ordinary mileposts almost everywhere.
- Age. Some layers are updated every year. Others were collected once and not refreshed.
All 50 states in one table
The MileCheck mile marker dataset combines the state layers into one schema.
- 396,842 marker positions on 9,056 signed routes, release of November 2, 2026.
- Fields include signed route, marker number, latitude, longitude, county, direction, source agency and the source's stated terms.
- CSV and GeoJSON, one file per state and one national file.
- A full refresh every month with a list of markers added, moved and removed.
It is sold as a flat yearly license from $5,000, with a free Washington and Oregon sample. See what is in it and ask for the sample.
Questions people ask
Where can I download mile marker data for one state?
Start with that state DOT's open data or GIS portal. Search for "mileposts" or "reference markers". Massachusetts, Virginia and Oregon, for example, publish theirs as open GIS layers.
Is there a national milepost dataset on data.gov?
Not for highways. A data.gov search for mileposts mostly returns the Federal Railroad Administration's rail mileposts and single-state or county layers. Highway mileposts are published by each state.
Do all states use the same mile marker system?
No. Interstates use mileposts almost everywhere, but California uses county-based postmiles and New York uses reference markers on state roads.
How many mile markers are there in the US?
The MileCheck dataset has 396,842 marker positions on 9,056 signed routes across the 50 states. Some markers appear twice, once for each side of the road, where the state publishes both.