Buying Land in Marion County, Illinois

Zoning: a Planning Division administers it, though details are incomplete

Marion County publishes a "Marion County Zoning" dataset on its own GIS open data portal, described as containing land-use classifications maintained by the Marion County Planning Division -- solid evidence the county has adopted and actively maintains zoning for unincorporated land. That said, this research pass could not independently confirm a dedicated Planning Division office phone number or address separate from the county's general offices, nor could it read the underlying zoning ordinance text directly. If a specific parcel's zoning classification or a building-permit question matters to your purchase, start with the Marion County Clerk's office (100 E. Main Street, Salem; (618) 548-3400) and ask to be directed to the Planning Division or Building Department, which handles building, land-use, and septic-related permits for unincorporated Marion County.

Marion County has 17 townships across 576 square miles (2020 population 37,729) and uses Illinois's standard township form of government rather than the commission form used by 17 of the state's 102 counties. Because the evidence points to the county having adopted countywide zoning, Illinois's Article 110 township zoning would not independently apply in any Marion County township under the state framework -- but confirm this directly with the county given the incomplete picture above, particularly if a specific township's own historical zoning status matters to your purchase.

The Salem oil field: briefly the second-largest in the country

The Salem oil field was discovered by The Texas Company on July 1, 1938, in Marion County farmland. Twelve months after discovery, the field had already produced 20,080,000 barrels of oil, and by the week of January 7, 1939, it ranked seventh in the entire United States for daily production. The boom accelerated fast: 93 million barrels of oil were pumped from Marion County's farmland in 1939 alone, at a time when producers were selling oil for roughly fifty cents a barrel. Production peaked in 1940 at 95.27 million barrels -- an average of roughly 261,000 barrels per day -- briefly making Salem the second-largest oil field in the United States. All of the field's producing formations are Mississippian in age, spanning the Benoist sand, the Aux Vases sand, and the McClosky oolitic limestone.

The scale of the transformation was dramatic for what had been, up to that point, a struggling agricultural economy: one resident recalled that before the boom, "we were like everyone else. We were farmers about to starve. It was lucky if we had enough money to pay taxes." President Franklin D. Roosevelt is reported to have said "Thank God for Salem, Illinois" in reference to the field's contribution to wartime fuel supply. By the end of the 1960s, though, the boom years were over, as national oil companies increasingly looked to Texas, New Mexico, and offshore fields, and Marion County's production entered a long decline that has continued, gradually, ever since.

Still active today: what a legacy oil county means for a modern land purchase

Marion County's oil history isn't purely historical. Kansas Geological Survey county-production data shows Marion County producing 94,496 barrels of oil from 259 active wells in 2020, declining to 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 -- a real, ongoing, if steadily declining, oil-production county. New well permits are still being issued; IDNR well-permit logs show, for example, a Carter #6 well permitted on April 3, 2025, operated by Ameren Illinois Company.

For a land buyer, that combination of deep history and continuing activity raises a few specific, checkable questions that most Illinois counties don't require. First, mineral rights: in Illinois, oil and gas rights can be, and frequently were during the boom era, severed from the surface estate -- meaning the person who owns the surface of a parcel may not own the oil and gas beneath it, and the mineral-estate owner generally has the right to access and develop those minerals, subject to the surface owner's right to "subjacent support" against damage. A title search and mineral-rights search are worth doing specifically, not just assumed to be clean, on any Marion County parcel with oil history. Second, legacy and abandoned wells: Illinois has an estimated statewide cleanup liability in the hundreds of millions of dollars tied to unplugged, abandoned, or orphaned oil wells, and Marion County -- given its production history -- is a place where checking a specific parcel against the Illinois State Geological Survey's ILOIL well-locator map (covering more than 200,000 recorded Illinois oil and gas wells) before you buy is a genuinely useful, low-cost step, not an abundance of caution. See our dedicated buying-land page for what to actually check.

Septic, GIS, and other departments to know

Septic (private sewage disposal) and water well permitting in Marion County runs through the Marion County Health Department's Division of Environmental Health (118 Cross Creek Boulevard, Salem; (618) 548-3878) under the statewide IDPH Title 77 Part 905 code. The Marion County Supervisor of Assessments (100 E. Main St., Room 101, Salem; (618) 548-3853) handles property valuation and works with individual township assessors, the Marion County Clerk & Recorder (100 E. Main St., Salem; (618) 548-3400) holds deed and plat records, and University of Illinois Extension serves Marion County jointly with Bond, Clinton, Jefferson, and Washington Counties, with an office reachable at (618) 548-1446 -- relevant to the county's substantial agricultural sector alongside its legacy oil production.