| 1 | A & G Oil & Gas | Shelby, MT 59474 | Oil & Gas Operator | Jul 2011 |
| 2 | A&S Mineral Development Company, LLC | Poplar, MT 59255 | Oil & Gas Operator | Jan 2025 |
| 3 | A. B. Energy LLC | Chester, MT 59522 | Oil & Gas Operator | Jan 2025 |
| 4 | Abraxas Petroleum Corporation | San Antonio, TX 78259 | Oil & Gas Operator | Mar 2025 |
| 5 | Aikins Drilling Company | Mohave Valley, AZ 86440 | Oil Operator | Dec 2019 |
| 6 | Ajax Oil Company | Billings, MT 59103 | Oil & Gas Operator | Dec 2003 |
| 7 | Alme, Henry A. | Cut Bank, MT 59427 | Gas Operator | Dec 2024 |
| 8 | Alta VIsta Oil Corporation | Clearmont, WY 82835 | Oil & Gas Operator | Jul 2021 |
| 9 | Altamont Oil & Gas Inc. | Cut Bank, MT 59427-0200 | Oil & Gas Operator | May 2012 |
| 10 | Alturas Energy LLC | Sidney, MT 59270 | Oil Operator | Mar 2022 |
| 11 | American Exploration Company | Houston, TX 77010 | Oil & Gas Operator | Jan 2000 |
| 12 | American Midwest Oil & Gas Corp. | Billings, MT 59101 | Gas Operator | Jun 2021 |
| 13 | Amoco Production Co. | Houston, TX 77253 | Oil & Gas Operator | Jun 2015 |
| 14 | Anadarko Minerals Inc | Oklahoma City, OK 73102 | Oil & Gas Operator | Jan 2025 |
| 15 | Anr Production Company | Houston, TX 77046 | Oil & Gas Operator | Aug 2017 |
| 16 | Ansbro Petroleum Company, LLC | Denver, CO 80202 | Oil & Gas Operator | Feb 2008 |
| 17 | Anschutz Exploration Corporation | Denver, CO 80202 | Oil & Gas Operator | Mar 2025 |
| 18 | Antelope Resources Inc | Billings, MT 59101 | Oil & Gas Operator | May 2017 |
| 19 | Apex Energy, L.L.C. | Tulsa, OK 74114 | Oil & Gas Operator | Dec 2024 |
| 20 | Armstrong Operating, Inc. | Dickinson, ND 58602 | Oil & Gas Operator | Jan 2025 |
| 21 | Artex Oil Company | Marietta, OH 45750 | Oil & Gas Operator | Dec 2023 |
| 22 | Assiniboine & Sioux Tribes | | Oil & Gas Operator | Mar 1997 |
| 23 | Athena Energy LLC | Toronto, ON M5E 1W7 | Gas Operator | Jan 2011 |
| 24 | Austin, Chas W | | Oil Operator | Jan 2009 |
| 25 | Aztec Gas And Oil Corporation | Elephant Butte, NM 87935-0370 | Oil & Gas Operator | Mar 2005 |