The finding
The United States Geological Survey keeps a federal file of mine sites, the Mineral Resources Data System. It holds 274,114 sites with a recorded position. Placing each of those positions inside the Census Bureau boundary files puts 15,600 worked out, prospected or recorded mine sites inside the limits of 3,496 American towns and cities, and 203,398 inside 2,516 counties.
The towns carrying the most are not abstractions. Joplin, Missouri, a city of about fifty thousand people, has 593 of them inside the city limits. Granby, Missouri, a town of two thousand, has 218, sixty three of which the federal file records as underground workings.
- Joplin, Missouri593 old or abandoned mine sites inside the town limits
- Iron River, Michigan220 old or abandoned mine sites inside the town limits
- Granby, Missouri218 old or abandoned mine sites inside the town limits
- Hibbing, Minnesota169 old or abandoned mine sites inside the town limits
- Aurora, Missouri145 old or abandoned mine sites inside the town limits
- Grass Valley, California138 old or abandoned mine sites inside the town limits
- Idaho Springs, Colorado121 old or abandoned mine sites inside the town limits
- Ester, Alaska119 old or abandoned mine sites inside the town limits
- Valdez, Alaska88 old or abandoned mine sites inside the town limits
- Cartersville, Georgia78 old or abandoned mine sites inside the town limits
Why it matters
Abandoned underground workings collapse. When the ground over a worked out room gives way the subsidence takes foundations, roads and sewer lines with it, and a standard homeowner policy does not cover it. Eight states run a separate mine subsidence insurance programme for exactly that reason.
The maps that show what runs under a given property exist. They are the surveys the mine operators filed, and they sit with state mining agencies and with the federal repository. What has not existed is a free, plain place for a householder to start: a search by address, and the name of the office to ask.
What is new here
Three things, all of them free and none of them behind a login.
- A search by ZIP code, by town or by street address that reads the federal mine file around that point and lists what is recorded, nearest first, with the distance and the USGS record for each site.
- The federal file crossed with the Census boundaries, so the count is given for a town and a county rather than for a map sheet.
- The office that holds the mine maps named for all fifty states and the District of Columbia, each one opened and read before it was listed, including the states that have no programme at all.
How it was done, and what it cannot do
Sources: the USGS Mineral Resources Data System, the federal file of named mines, downloaded whole; the USGS topographic mine features, 466,747 shafts, adits, pits and mines digitised from the historical topographic sheets; the Census Bureau TIGER place and county boundary files for 2024; the Census Bureau gazetteer for ZIP code and place centres; and the Census Bureau geocoder for a street address. Every point was placed inside a boundary by its own coordinates, not by the county name written in the file, because all 12,958 Alaska records in the mineral file carry no county name at all.
Everything here can be wrong. Information, not a guarantee. The two federal files can be wrong, incomplete or out of date, a point is a location and not a property line, and nothing published here says that a mine is or is not under any particular property. No one should buy, sell, move or make any decision about a home on this alone: the state mine map office holds the maps and a qualified engineer reads the ground.
Why two files, stated plainly: the mineral file holds almost no coal, 157 coal records in the whole country and none in Pennsylvania, West Virginia or Illinois. On its own it would show Scranton with a single sand pit. The topographic features are where the coal openings are, 97,226 shafts, adits and tunnels nationwide, each with the sheet and the survey year, so the two together are the first free national layer that covers both the metal districts of the West and the coal towns of the East.
What it cannot do, stated plainly: this does not tell anyone that a mine runs under their house. A record in the federal file is a point with a position of varying precision, not a survey of the workings. Only the mine map shows what runs under a given parcel, and only the state mine map office or the federal repository holds it. A search that finds nothing is not a clearance either: the file records mine sites, not every working ever driven.
What a householder does with it
Search the address. Then take the result to the office that holds the maps for that state. Two states make it easy. Pennsylvania DEP runs an address lookup that says whether a site falls inside a known underground mining area at gis.dep.pa.gov/msiRisk. Ohio publishes a mines locator that takes a street address at the ODNR mines locator, and its mine subsidence insurance is added to every homeowner policy for one dollar a year in twenty six counties. Wyoming has no viewer at all and tells people to telephone its abandoned mine land division. Mississippi states that it has no underground mines.
The data, for anyone who wants to check it
Nothing here is ours to own. The mine file is a federal public record and the boundaries are federal public records. The figures above can be rebuilt from the two downloads below.
- USGS Mineral Resources Data System, whole fileThe federal mine file as a CSV, 25.8 MB
- Census Bureau TIGER place boundariesThe town and city limits used to place each site
- OSMRE National Mine Map RepositoryThe federal collection of filed underground mine maps
The map image on this page may be reproduced with the line: Source, USGS Mineral Resources Data System and the Census Bureau, mapped by PublicRecordCenter.com.