Reference

Pennsylvania API county codes

Every Pennsylvania API well number starts with 37, the state code. The next three digits are the county code, one of the 67 listed below, so a number beginning 37-001 belongs to a well in Adams County.

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

How to read a Pennsylvania API number

37State: Pennsylvania
001County: Adams
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 67 Pennsylvania counties

County code County API numbers start
001 Adams 37-001-
003 Allegheny 37-003-
005 Armstrong 37-005-
007 Beaver 37-007-
009 Bedford 37-009-
011 Berks 37-011-
013 Blair 37-013-
015 Bradford 37-015-
017 Bucks 37-017-
019 Butler 37-019-
021 Cambria 37-021-
023 Cameron 37-023-
025 Carbon 37-025-
027 Centre 37-027-
029 Chester 37-029-
031 Clarion 37-031-
033 Clearfield 37-033-
035 Clinton 37-035-
037 Columbia 37-037-
039 Crawford 37-039-
041 Cumberland 37-041-
043 Dauphin 37-043-
045 Delaware 37-045-
047 Elk 37-047-
049 Erie 37-049-
051 Fayette 37-051-
053 Forest 37-053-
055 Franklin 37-055-
057 Fulton 37-057-
059 Greene 37-059-
061 Huntingdon 37-061-
063 Indiana 37-063-
065 Jefferson 37-065-
067 Juniata 37-067-
069 Lackawanna 37-069-
071 Lancaster 37-071-
073 Lawrence 37-073-
075 Lebanon 37-075-
077 Lehigh 37-077-
079 Luzerne 37-079-
081 Lycoming 37-081-
083 McKean 37-083-
085 Mercer 37-085-
087 Mifflin 37-087-
089 Monroe 37-089-
091 Montgomery 37-091-
093 Montour 37-093-
095 Northampton 37-095-
097 Northumberland 37-097-
099 Perry 37-099-
101 Philadelphia 37-101-
103 Pike 37-103-
105 Potter 37-105-
107 Schuylkill 37-107-
109 Snyder 37-109-
111 Somerset 37-111-
113 Sullivan 37-113-
115 Susquehanna 37-115-
117 Tioga 37-117-
119 Union 37-119-
121 Venango 37-121-
123 Warren 37-123-
125 Washington 37-125-
127 Wayne 37-127-
129 Westmoreland 37-129-
131 Wyoming 37-131-
133 York 37-133-

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. In Pennsylvania that is the eMapPA, run by the Pennsylvania Department of Environmental Protection (DEP).

For what the Pennsylvania public records hold in total, see the Pennsylvania oil and gas data summary.

Frequently asked questions

What is the API state code for Pennsylvania?

37. 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 Pennsylvania API number?

Read digits three to five and find them in the table on this page. In 37-001-12345, the county code is 001, which is Adams County. If the code is missing from the table, it is usually an offshore area rather than an onshore county.

Does a Pennsylvania 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.

Every Pennsylvania well, on one map

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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). Pennsylvania API county codes. Reference generated 2026-09-24. https://tetrasoftco.com/tools/api-county-codes/pennsylvania/