Reference

Montana API county codes

Every Montana API well number starts with 25, the state code. The next three digits are the county code, one of the 56 listed below, so a number beginning 25-001 belongs to a well in Beaverhead County.

To decode a whole number, including the sidetrack and completion digits, paste it into the API well number decoder.

How to read a Montana API number

25State: Montana
001County: Beaverhead
12345Well, unique within the county

The first ten digits identify one well. Two more digits can follow for a sidetrack, and two after that for a later completion. The county is the one where the well starts at the surface, so a horizontal well that crosses a county line keeps its surface county's code. A few state regulators assign the producing county instead, so the state record is the final word on a well near a boundary.

All 56 Montana counties

County code County API numbers start
001 Beaverhead 25-001-
003 Big Horn 25-003-
005 Blaine 25-005-
007 Broadwater 25-007-
009 Carbon 25-009-
011 Carter 25-011-
013 Cascade 25-013-
015 Chouteau 25-015-
017 Custer 25-017-
019 Daniels 25-019-
021 Dawson 25-021-
023 Deer Lodge 25-023-
025 Fallon 25-025-
027 Fergus 25-027-
029 Flathead 25-029-
031 Gallatin 25-031-
033 Garfield 25-033-
035 Glacier 25-035-
037 Golden Valley 25-037-
039 Granite 25-039-
041 Hill 25-041-
043 Jefferson 25-043-
045 Judith Basin 25-045-
047 Lake 25-047-
049 Lewis and Clark 25-049-
051 Liberty 25-051-
053 Lincoln 25-053-
055 McCone 25-055-
057 Madison 25-057-
059 Meagher 25-059-
061 Mineral 25-061-
063 Missoula 25-063-
065 Musselshell 25-065-
067 Park 25-067-
069 Petroleum 25-069-
071 Phillips 25-071-
073 Pondera 25-073-
075 Powder River 25-075-
077 Powell 25-077-
079 Prairie 25-079-
081 Ravalli 25-081-
083 Richland 25-083-
085 Roosevelt 25-085-
087 Rosebud 25-087-
089 Sanders 25-089-
091 Sheridan 25-091-
093 Silver Bow 25-093-
095 Stillwater 25-095-
097 Sweet Grass 25-097-
099 Teton 25-099-
101 Toole 25-101-
103 Treasure 25-103-
105 Valley 25-105-
107 Wheatland 25-107-
109 Wibaux 25-109-
111 Yellowstone 25-111-

County names are the US Census names for these codes. The API standard does not promise the two match, so we checked them against state well records. Across 35 states, where this table names a county it matched the one the agency recorded on 85,091 of 85,100 wells. Offshore state and federal waters use their own pseudo-county codes, which are not listed here.

Finding the well itself

The API number stops at the county. It does not hold the well's coordinates, lease, survey section or operator. Those sit in the well record, which you find by searching the full number in the state agency's system. Search it at the Montana oil and gas regulator.

Frequently asked questions

What is the API state code for Montana?

25. API state codes run alphabetically from 01 for Alabama to 49 for Wyoming, then 50 for Alaska and 51 for Hawaii. They are not the Census FIPS state codes, which is a common source of wrong lookups.

How do I find the county from a Montana API number?

Read digits three to five and find them in the table on this page. In 25-001-12345, the county code is 001, which is Beaverhead County. If the code is missing from the table, it is usually an offshore area rather than an onshore county.

Does a Montana API number give the well's exact location?

No. The number stops at the county. Coordinates, the lease and the survey location are in the well record held by the state agency, which you search with the full API number.

State codes: American Petroleum Institute Bulletin D12A well numbering standard. County names: US Census county FIPS names, checked against state well records. Reference generated .

How to cite this page

Sources: American Petroleum Institute Bulletin D12A well numbering standard; US Census county FIPS codes.

TetraSoft. (2026). Montana API county codes. Reference generated 2026-09-24. https://tetrasoftco.com/tools/api-county-codes/montana/