Abandoned mines in California
California has 57,618 mine and prospect features on USGS topographic maps published 1896–2004, including 18,668 mine openings (shafts, adits and air shafts), across 57 counties. OSMRE's abandoned mine land inventory lists 15 problems in the state, 6 of them not yet reclaimed. MSHA's register carries 2,013 California mines with status Abandoned or Abandoned and Sealed.
Every mine and prospect feature the USGS digitized from historical topographic maps of California, every OSMRE abandoned mine land problem, and every MSHA-registered mine with status Abandoned, by county. Each county page lists the named features and links every MSHA mine to its own record.
- Mapped mine features (USGS)
- 57,618
- Mine openings
- 18,668
- OSMRE problems unreclaimed
- 6
- MSHA mines marked abandoned
- 2,013
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18,678 32.4%Mine openingsshafts, adits, air shafts, portals and vertical openings: the ways into underground workings
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27,462 47.6%Prospect pits and trenchesshallow exploration diggings that never became a mine
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3,766 6.5%Mines and surface workingslabelled mines, open pits, strip mines, placer and hydraulic workings
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5,429 9.4%Quarries, gravel and borrow pitsconstruction-material and industrial-mineral extraction
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2,284 4.0%Dumps, tailings, spoil and gobwhat mining left above ground
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11 0.0%Mills, tipples and facilitiesprocessing plants and hazardous structures
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3 0.0%Other reclamation problemshighwalls, subsidence, polluted or clogged water, fires, slides and gases in OSMRE's inventory
| Feature type | Features |
|---|---|
| Prospect Pit | 27,415 |
| Adit | 11,049 |
| Mine Shaft | 7,617 |
| Open Pit Mine | 1,695 |
| Gravel Pit | 1,400 |
| Open Pit Mine or Quarry | 1,138 |
| Tailings - Undifferentiated | 993 |
| Borrow Pit | 936 |
| Quarry | 854 |
| Gravel Pit | 631 |
| Tailings - Dredge | 438 |
| Salt Evaporator | 403 |
| Gravel/Borrow Pit - Undifferentiated | 346 |
| Open Pit Mine | 336 |
| Mine Dump | 315 |
| Borrow Pit | 297 |
| Quarry | 203 |
| Disturbed Surface | 170 |
| Cinder Pit | 169 |
| Clay Pit | 126 |
| Mine | 119 |
| Sand Pit | 113 |
| Disturbed Surface - Pit | 107 |
| Tailings - Pond | 104 |
| Gravel/Borrow Pit - Undifferentiated | 82 |
| Sand Pit | 73 |
| Diggings | 69 |
| Clay Pit | 54 |
| Cinder Pit | 51 |
| Trench | 47 |
| Strip Mine | 42 |
| Placer Mine | 24 |
| Diggings | 22 |
| Quarry - Rock | 20 |
| Open Pit Mine or Quarry | 19 |
| Quarry - Pumice | 17 |
| Quarry - Pumice | 16 |
| Evaporation Pond | 15 |
| Hydraulic Mine | 13 |
| Mill Site | 11 |
A USGS feature is a symbol on a historical topographic map, there when the map was surveyed; it may since have been sealed, reclaimed, built over or reopened, and the map does not say which. An OSMRE row is a problem the abandoned mine land program tracks, not a mine, and several problems make one problem area (PAD), which is the unit a state program counts and reports; the public extract can also hold more problem areas than a state's live inventory, because areas since merged or ruled ineligible stay in the published file, so a state figure that differs from this one is not a contradiction. An MSHA mine is a registered operation whose operator reported abandonment, a record that starts in the 1970s; that is a regulatory status rather than a physical one, and it also holds operations merely between jobs, portable crushers above all, which is why over a thousand mines carrying it have been inspected in the last two years. The three overlap and are never added together. Counties are assigned from each feature's coordinates against the Census 2023 county boundaries. The full method and every source are on the national page.
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USGS, Consolidated Prospect- and Mine-Related Features from 7.5- and 15-Minute Topographic Quadrangle Maps of the United States (USMIN)
597,612 point and area features digitized from about 106,350 historical topographic maps published 1886–2006; public domain (CC0). A feature is a map symbol, not a field-verified site, and the map does not say whether it was still worked.
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USGS Fact Sheet 2025–3003, The Abandoned Mine Inventory of the United States
States that as of 2025 there is no comprehensive national inventory of abandoned mine features, and that the detailed national database now being built will not be published.
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OSMRE, Abandoned Mine Land Inventory System (e-AMLIS), public Problems layer
One row per abandoned mine land problem in a problem area, with its type, funding program and reclamation status; mostly coal mined before the 1977 Surface Mining Control and Reclamation Act. Coordinates are the problem area's.
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MSHA, Mines dataset (Mine Data Retrieval System)
Every mine registered with MSHA since the 1970s; a mine reads Abandoned or Abandoned and Sealed when its operator reported that status. Refreshed weekly.
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US Census Bureau, 2023 cartographic county boundaries (1:500,000)
Each feature's county is assigned by its coordinates against these boundaries, not copied from the source file.
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GAO-20-238, Abandoned Hardrock Mines (March 2020)
Federal agencies had identified at least 140,000 abandoned hardrock mine features on federal land and estimated more than 390,000 more not yet captured in their databases.
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Abandoned Hardrock Mine Reclamation (AHMR) Program, US Department of the Interior
The program the USGS inventory is compiled for. Its appropriations and the 674,000 field-confirmed feature count on this page were provided by the program manager, Office of Environmental Policy and Compliance, and are cited with permission (2026-09-08).
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IMCC-NAAMLP Hardrock AML Report
Page 48 carries the two figures this page leans on: USGS estimates 633,181 of the 725,690 mine features it recorded from historic topographic maps, 87 percent, are hardrock; and state and federal agencies have submitted more than 724,000 AML features to the national database being built, already more than the historic maps hold. Year-by-year AHMR funding is on page 35.