Buying Land in Marion County, Illinois: What a Legacy (and Still-Active) Oil County Means for You

A boom that briefly made Marion County a national oil story

The Salem oil field was discovered by The Texas Company on July 1, 1938. Within a year, the field had produced more than 20 million barrels, and by early 1939 it ranked seventh nationally for daily production. The boom peaked in 1940 at 95.27 million barrels -- an average of roughly 261,000 barrels a day -- briefly making Salem the second-largest oil field in the United States. In 1939 alone, 93 million barrels came out of Marion County farmland, at fifty cents a barrel. All of the field's producing formations are Mississippian in age: the Benoist sand, the Aux Vases sand, and the McClosky oolitic limestone.

The transformation was as much social as economic. One longtime resident recalled that before the boom, area farmers were "about to starve," barely able to cover their taxes. President Franklin D. Roosevelt is reported to have said "Thank God for Salem, Illinois," crediting the field's output with helping fuel the country through World War II. By the end of the 1960s, national oil companies had largely turned their attention to Texas, New Mexico, and offshore fields, and Marion County's production entered a long, steady decline -- but, notably, it never fully stopped.

It's not history -- Marion County still has active wells today

Kansas Geological Survey county-production data, which aggregates Illinois's own state production records, shows Marion County producing 94,496 barrels of oil from 259 active wells in 2020, 89,722 barrels from 213 wells in 2023, 81,702 barrels from 166 wells in 2024, and 57,602 barrels from 147 active wells as of September 2025. That's a real, ongoing, if declining, production county -- not a museum piece. New permits are still being issued, too: IDNR well-permit logs list, for example, a Carter #6 well permitted on April 3, 2025, operated by Ameren Illinois Company. If you're evaluating raw land or farmland in Marion County, it's worth treating oil activity as a live possibility, not a settled question from 80 years ago.

Mineral rights: check whether they were severed from the surface

Illinois law allows mineral rights -- including oil and gas -- to be severed from the surface estate, meaning the person who owns the surface of a parcel doesn't automatically own what's underneath it. Severance happens either by a direct conveyance of the mineral rights alone, or by a landowner selling the surface while reserving the minerals for themselves; either way, it creates two distinct, independently taxable estates in the same land. In a legacy oil county like Marion, where boom-era landowners frequently sold or leased mineral rights separately from the surface during the 1938-1940s rush, a title search that only confirms surface ownership can miss this entirely.

The practical consequence: if the mineral estate under your parcel is owned separately, the mineral owner (or their lessee) generally retains the right to access and develop those minerals -- drill a new well, maintain an existing one, run access roads or pipelines -- subject to the surface owner's right to "subjacent support" (protection against the land itself subsiding or collapsing from extraction). Illinois's Severed Mineral Interest Act does allow a surface owner to make an adverse-possession claim against a missing or unknown mineral-rights holder under specific conditions, but that's a legal process, not something to assume applies to your parcel by default. A title search or an Illinois real-estate attorney experienced in oil and gas can tell you definitively whether a specific Marion County parcel has a severed mineral estate, and if so, who currently holds it.

Legacy and abandoned wells: check before you buy, not after

Illinois's decades-long oil boom left a real, statewide legacy problem: an estimated $160 million cleanup bill tied to wells that were abandoned, orphaned, or never properly plugged, with the burden increasingly falling on the state -- or, in some cases, the surface landowner -- when the original operator can no longer be found or held responsible. IDNR's Office of Oil and Gas Resource Management runs a Plugging and Restoration Fund (established 1991, funded through fees and forfeited bonds) to plug wells that meet the definition of an emergency, orphan, or abandoned well, and a separate Landowner Grant Program specifically helps plug abandoned wells on private property -- but only wells that have gone through an administrative order declaring them abandoned qualify.

Before buying a Marion County parcel, particularly one with any visible well pad, pipe, tank battery, or unexplained clearing, check the Illinois State Geological Survey's ILOIL Oil and Gas Resources Map -- an interactive tool covering more than 200,000 recorded Illinois oil and gas well locations -- to see whether any wells (active, plugged, or unaccounted-for) sit on or near the parcel. An unplugged well that isn't visible at the surface can still be there; a wellbore that was plugged decades ago under older standards can still pose an environmental or liability question worth raising with a specialist before closing.

• Check the ISGS ILOIL map for the specific parcel, not just the general township or community
• Ask a title company or Illinois oil-and-gas attorney to confirm whether the parcel's mineral rights are severed from the surface, and if so, who currently holds them
• For a parcel with any visible well infrastructure, ask IDNR's Office of Oil and Gas Resource Management directly about that well's current permit status (active, plugged, or orphaned)
• If an active well or lease exists on the parcel, review the surface-use agreement or lease terms carefully -- these govern access roads, pipeline easements, and royalty payments, and typically transfer with the land unless specifically addressed in your purchase contract

Bottom line

None of this means Marion County land is unusually risky -- most of the county functions as ordinary south-central Illinois farmland, and hundreds of active wells coexist with agriculture across the county every day. But the specific due-diligence checklist here is different from a county with no oil history: a mineral-rights check and an ILOIL well-map check are both concrete, low-cost steps worth taking on any Marion County parcel before you close, precisely because this county's oil legacy is real, current, and still evolving rather than a settled piece of the past.