Where to look it up · the ten biggest producing states
Every state has a Railroad Commission. Only one of them calls it that.
If your minerals are in Texas, one free state website will tell you who drilled your well, where the unit lines run, and what it has produced every month since it was completed. Move one state over and the agency has a different name, a different boss, and sometimes doesn't hold the document you need at all. Here is who to ask — and the single thing worth pulling — in the ten states that produce the most oil and gas.
Start here
First — what is a conservation agency?
Almost every oil and gas state has one agency that decides where wells may be drilled, how close together, and who shares the production. The name changes from state to state — Commission, Division, Department, Office — but the job is the same, and it is unusually useful to a mineral owner. To do that job, the agency has to make operators file things: where the well is going, what acreage it is assigned to, and how much it produced last month. Those filings are public. Reading them is how you check the arithmetic on your own check.
The agency does not hold your deed, does not hold your lease, and cannot tell you what you own. Ownership lives at the courthouse. What the agency holds is the well and the unit — which is exactly the half of the picture that is hardest to reconstruct on your own.
The map
Ten states, three kinds of agency
These ten states produce the overwhelming majority of American oil and gas. Ranked by oil and gas combined on a six-to-one barrel-of-oil-equivalent basis, using the Energy Information Administration's 2023 state production figures. What separates them, for a mineral owner, is not size — it is whether the state itself creates and records your unit, or leaves it to private contract.
Click any highlighted state
Who holds the records where you own
This is a grid map, not a survey map — every state is the same square, arranged in roughly the right places. It is drawn that way on purpose: the point here is which bucket a state is in, and a real outline map would invite you to read a precision into it that isn't there.
The ten
Who to ask, and the one thing to pull
Each state has its own page: what the agency is, where it came from, the single most useful document a mineral owner can pull from it and how to get there, what else is worth knowing, and where it differs from Texas.
Side by side
The four questions that change the most from state to state
| State | Agency | Pooling / unitization | Ad valorem on minerals | Records | Ownership records at |
|---|---|---|---|---|---|
| Texas | RRC | Pooling: mostly by lease | Ad valorem: yes | Free | County Clerk |
| Pennsylvania | DEP | No general pooling | No severance tax | Free | County Recorder of Deeds |
| New Mexico | OCD | Compulsory pooling: common | Ad valorem: withheld | Free | County Clerk |
| Louisiana | Office of Conservation | Compulsory unitization | Parish assessment | Free | Parish Clerk of Court |
| Oklahoma | OCC | Forced pooling: heavily used | Ad valorem: no | Free | County Clerk |
| North Dakota | NDIC | Pooling orders required | Ad valorem: no | Partly paid | County Recorder |
| West Virginia | WVDEP | Horizontal unitization (2022) | Ad valorem: yes | Free | County Clerk |
| Colorado | ECMC | Statutory pooling | Ad valorem: yes | Free | County Clerk and Recorder |
| Ohio | DOGRM | Unitization at 65% | Ad valorem: yes | Free | County Recorder |
| Wyoming | WOGCC | Spacing & pooling orders | Ad valorem: yes | Free | County Clerk |
A standing caution on the tax column. Whether a state bills a mineral owner a county property tax, or takes a production tax instead, or does both, is genuinely messy — reputable published sources contradict each other on several of these states. The column above records the structure as we understand it, not a rate, and it is the one thing on this page most worth confirming with the state's own revenue department or your own CPA before you rely on it. The severance tax versus ad valorem tax concept explains why the two are so easy to confuse in the first place.
How this happened
Why they all look alike — and why Pennsylvania doesn't
The striking thing about these agencies is not that every state has one. It is that they all use the same handful of words: waste, correlative rights, spacing, proration. That is not a coincidence, and it is not convergent evolution. They were copied from a common model, written in a single room, in response to a single disaster.
Pennsylvania is outside the story entirely — and by a long way. The American oil industry began there in 1859, thirty-two years before Texas even created the Railroad Commission and seventy-six years before the model conservation statute was drafted. Pennsylvania boomed, peaked and declined before the conservation-agency idea existed. By the time it might have adopted one, its oil fields were a century old and its law had already been settled by courts rather than commissions. So when the Marcellus arrived in the late 2000s, Pennsylvania had no conservation commission to hand it to. It handed it to an environmental agency instead — and that is why, alone among these ten states, it still has no general compulsory pooling.
1859Drake drills at Titusville, Pennsylvania
The first commercial oil well in the United States. For the next three decades Pennsylvania is the American oil industry — and it is governed by nothing but the rule of capture and the common law.
1891Pennsylvania peaks — the same year Texas creates the Railroad Commission
Two states, two completely different moments. Pennsylvania's oil production tops out; Texas establishes a commission to regulate railroad rates, with no thought of oil at all.
1901Spindletop
Texas's first great gusher, forty-two years after Drake. The centre of the industry starts moving southwest, into states with no oil law of their own yet.
1917–1919The Railroad Commission becomes an oil agency
In 1917 the Texas legislature declares oil and gas pipelines common carriers under the Commission. In March 1919, with production rising fast, it enacts a conservation statute forbidding waste and hands the Commission jurisdiction over the industry. The name never changed. Rail regulation left the agency for good in 2005, and no other state kept the label — Texas is the last Railroad Commission standing.
1930–31East Texas — and the collapse
The largest field yet found floods the market. Crude falls to pennies. Operators drain each other's leases under the rule of capture as fast as they can, because oil left in the ground is oil someone else will produce. Both Texas and Oklahoma end up putting oil fields under martial law.
1935The Interstate Compact to Conserve Oil and Gas
On 16 February 1935, representatives of Arkansas, California, Colorado, Illinois, Kansas, Michigan, New Mexico, Oklahoma and Texas met in Dallas and wrote a compact "to conserve oil and gas by the prevention of physical waste thereof from any cause." Congress approved it on 27 August. The commission set up to carry it out still exists, in Oklahoma City. This is the moment every agency on this page traces back to — the shared vocabulary of waste, correlative rights and spacing comes from here.
1951Wyoming adopts the model
The Wyoming Oil and Gas Conservation Act creates the WOGCC and charges it with preventing waste and protecting correlative rights — sixteen years after the compact, in nearly the same words. Other states did the same thing on their own timetables.
1961Pennsylvania passes a conservation law — for deep wells only
Pennsylvania's Oil and Gas Conservation Law does allow spacing and pooling orders, but only reaches wells drilled below the Onondaga horizon. It has almost nothing to do with the shallow fields, and nothing at all to do with the Marcellus.
1968Every well in the country gets a number
The American Petroleum Institute publishes Bulletin D12A, defining the API well number. The recommendation is that the states, not any federal body, assign the numbers as part of permitting — which is exactly what happened, and why there is still no single national well database.
2008The Marcellus arrives — 149 years after Drake
Horizontal drilling reopens Pennsylvania on a scale nobody anticipated. There is no conservation commission to send it to, so it goes to the Department of Environmental Protection, created in 1995. Operators have to assemble units the old way: by getting every owner to sign.
2010–2011The number changes hands; a national registry appears
API concludes well numbering is no longer its job and transfers custody of the standard to the PPDM Association. In April 2011 the Ground Water Protection Council and the Interstate Oil and Gas Compact Commission — the direct descendant of the 1935 compact — launch FracFocus, the closest thing to a national well registry that exists.
2022–2023The map keeps moving
West Virginia enacts horizontal well unitization, giving its owners a filing that names them. Colorado renames its agency the Energy and Carbon Management Commission, adding carbon storage and deep geothermal to a body that had regulated oil and gas for seventy-two years. Neither of these is finished changing.
The federal picture
Is anyone tracking all of this nationally?
Not really — and the reason is a decision made in the 1960s. When the industry set out to give every American well a unique number, the recommendation was that the numbers be assigned by the state agencies that already ran permitting. That is what happened. The result is a genuinely national standard with no national database: the API number works in all fifty states, but you still have to know which state's website to type it into.
Custody of the standard itself has moved. API published the specification in 1968 and last revised it in 1979; in 2010 it concluded that well numbering was no longer within its mission and transferred the standard to the PPDM Association, which published a successor called the US Well Number Standard. Offshore, the federal regulator assigns the number when it approves the permit. Onshore, your state does.
The one number that works everywhere
Take an API number apart
Step the arrows · tap a scenario
Texas
Loving Co.
of numbering
(wellbore)
(completion)
The first two digits are the state, the next three the county or parish, and the next five are that well's place in the order the county numbered its wells. The last two pairs are optional: the first records sidetracks off the original hole, the second records later completions. County codes in every state shown here line up with the federal FIPS county code — but each state's assigning authority publishes its own list, and Kern County, California ran out of its 99,999 well numbers and had to be given a second county code entirely.
There are four things that come close to being national, and all four are free:
The point that trips everyone up
"The state regulates oil and gas, so the state must know what I own." It doesn't, and it never did. These agencies exist to prevent waste and keep operators honest with each other — not to keep a register of mineral owners. What they hold is the well and the unit: where it was drilled, what acreage it was assigned, what it produced. Your ownership lives somewhere else entirely, in the deed records at the county clerk, recorder, or parish clerk of court. Almost every frustrating afternoon a mineral owner spends on a state website comes from asking it the one question it was never built to answer.
Every fact on these pages was checked against the agency's own site or the statute behind it, and the production ranking against EIA data. Even so: agencies rename themselves, forms get renumbered, fee schedules change, and links rot. If something here is out of date, the agency's own site wins — and it would be a kindness to say so.