Abandoned mines in San Luis Obispo County, California

1. Mine openings

   shafts, adits, air shafts, portals and vertical openings: the ways into underground workings
   21 5.8%
2. Prospect pits and trenches

   shallow exploration diggings that never became a mine
   113 31.4%
3. Mines and surface workings

   labelled mines, open pits, strip mines, placer and hydraulic workings
   80 22.2%
4. Quarries, gravel and borrow pits

   construction-material and industrial-mineral extraction
   144 40.0%
5. Dumps, tailings, spoil and gob

   what mining left above ground
   2 0.6%

A name is the label printed beside the symbol on the map. "First mapped" is the earliest topographic edition that shows the symbol, which bounds the feature's age from above; it is not the date it was worked. Unnamed features (most prospect pits, adits and shafts carry no label) are in the counts above but not this list.

1. Alamo Rock

   Surface metal/non-metal · Alamo Rock Company · MSHA ID 0404215
   Abandoned 1993-07-15
2. Bianchi Pit

   Surface metal/non-metal · Winsor Construction · MSHA ID 0404914
   Abandoned 1988-10-26
3. California Valley Community Services Gra

   Surface metal/non-metal · California Community Services Gravel · MSHA ID 0404398
   Abandoned 1982-07-29
4. California Valley Gyp Pit

   Surface metal/non-metal · W-R Gypsum · MSHA ID 0404359
   Abandoned 1986-06-25
5. Carrizo Plains Mine

   Surface metal/non-metal · Fannin-Superior Gypsum Company · MSHA ID 0404336
   Abandoned 1980-08-18
6. Cary Pit

   Surface metal/non-metal · Viborg Sand & Gravel Inc · MSHA ID 0405074
   Abandoned 1990-06-19
7. Dirtman Sand & Gravel #2

   Surface metal/non-metal · Dirtman Trucking · MSHA ID 0404851
   Abandoned 1992-05-19
8. Farming Camp Mine

   Surface metal/non-metal · Temblor Gypsum Company · MSHA ID 0404565
   Abandoned 1986-06-25
9. Gilbreath Gypsum Incorporated

   Surface metal/non-metal · Gilbreath Gypsum Inc · MSHA ID 0404190
   Abandoned 1984-06-27
10. Guerra Pit

    Surface metal/non-metal · Robert Guerra · MSHA ID 0400120
    Abandoned 1979-06-19
11. KRITZ/GOSS

    Surface metal/non-metal · Kritz Excavating & Trucking Inc · MSHA ID 0404994
    Abandoned 2001-03-03
12. LOMPOC PLANT

    Facility metal/non-metal · Grefco Minerals Inc · MSHA ID 0402846
    Abandoned 1999-08-27
13. Lone Oak Rock & Sand

    Surface metal/non-metal · Lone Oak Rock & Sand · MSHA ID 0405072
    Abandoned 1994-03-30
14. Morro Bay Plant

    Surface metal/non-metal · Pioneer Transit Mix Inc · MSHA ID 0403834
    Abandoned 1979-06-19
15. Morro Bay Plant

    Surface metal/non-metal · Pioneer Transit Mix Inc · MSHA ID 0404232
    Abandoned 1979-06-19
16. Morro Rock & Sand

    Surface metal/non-metal · Morro Rock & Sand Inc · MSHA ID 0401864
    Abandoned 1996-03-08
17. MUNARI PIT

    Surface metal/non-metal · Weyrick Companies · MSHA ID 0405093
    Abandoned 1998-03-26
18. Newhall Quarry

    Surface metal/non-metal · Granite Construction Company · MSHA ID 0404534
    Abandoned 1985-04-23
19. Paso Pit And Mill

    Surface metal/non-metal · Paso Constructors Inc · MSHA ID 0401905
    Abandoned 1982-07-29
20. PORTABLE PLANT D

    Surface metal/non-metal · Aman Brothers Inc · MSHA ID 0404845
    Abandoned 2001-04-30
21. River Sand & Gravel

    Surface metal/non-metal · River Sand & Gravel Inc · MSHA ID 0404924
    Abandoned 1991-09-23
22. Rodriques Pit

    Surface metal/non-metal · Bickford Concrete Inc · MSHA ID 0403480
    Abandoned 1979-06-19
23. Salinas Sand

    Surface metal/non-metal · Salinas Sand · MSHA ID 0405037
    Abandoned 1991-12-31
24. San Luis Brick Plant

    Surface metal/non-metal · San Luis Brick Inc · MSHA ID 0400603
    Abandoned 1979-06-27
25. San Simeon Mill

    Facility metal/non-metal · Lindseys San Simeon Gravel Company · MSHA ID 0403174
    Abandoned 1979-06-19
26. Santa Maria Pit And Mill

    Surface metal/non-metal · Santa Maria Sand Company · MSHA ID 0403814
    Abandoned 1991-10-23
27. Schlegel North County Sand & Gravel, Inc

    Surface metal/non-metal · Schlegel North County Sand & Gravel, Inc. · MSHA ID 0405370
    Abandoned 2014-05-29
28. Smith Sand Pit

    Surface metal/non-metal · Viborg Sand & Gravel, Inc. · MSHA ID 0405647
    Abandoned 2024-05-27
29. Templeton Hot Plant

    Surface metal/non-metal · Madonna Construction Company · MSHA ID 0402690
    Abandoned 1988-08-05
30. Weyrick Plant

    Surface metal/non-metal · Weyrick Sand & Gravel · MSHA ID 0405859
    Abandoned 2015-07-16

Status and date are as reported to MSHA by the operator. Each mine's own page carries its accident, citation and inspection record.

• San Bernardino County 14,976
• Inyo County 11,475
• Kern County 4,879
• Riverside County 3,227
• Mono County 2,946
• Siskiyou County 2,362
• Imperial County 1,232
• Mariposa County 1,079
• Tuolumne County 948
• San Diego County 901
• Calaveras County 840
• Shasta County 832

1. 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.
2. 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.
3. 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.
4. 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.
5. 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.
6. 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.
7. 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).
8. 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.