# Jefferson County, Illinois: Power, Data Centers and the Local Economy Home to Mount Vernon, Mount Vernon Township and Shiloh Township Jefferson County is where a large share of Illinois's next power plants are planned. Jefferson County is home to Mount Vernon, Mount Vernon Township, Shiloh Township and Dodds Township. 155 MW of new generation is planned here across 2 units, led by RWE Clean Energy (solar). 155 MW of it is already under construction or built. 2 MW of that came online in 2019 or later, mostly solar. Its power plants have 2 MW of capacity, 100% of it solar. Employers here counted 19,432 jobs in 2025, down 2.4% from 2019. 155 MW of new generation planned here, solar leading 2 MW of operating power plants, mostly solar -2.4% total jobs since 2019, now 19,432 ## Cities and towns in Jefferson County Jefferson County is home to Mount Vernon, Mount Vernon Township, Shiloh Township and Dodds Township. Mount Vernon14,187 residents Mount Vernon Township12,192 residents Shiloh Township6,449 residents Dodds Township2,682 residents Spring Garden Township2,522 residents Webber Township2,095 residents Rome Township1,624 residents Ina1,612 residents Field Township1,489 residents McClellan Township1,188 residents Casner Township1,141 residents Pendleton Township1,133 residents Grand Prairie Township886 residents Bald Hill Township781 residents Elk Prairie Township673 residents Woodlawn611 residents Bluford607 residents Farrington Township566 residents Dix456 residents Waltonville406 residents Blissville Township374 residents Bonnie365 residents Moores Prairie Township352 residents Belle Rive307 residents And 1 smaller places. Unincorporated communities (governed by the county): Opdyke. Residents are 2025 Census estimates for the part of each city, town or township inside this county. Census publishes no annual estimate for unincorporated communities. ## What changed in Jefferson County | Measure | Then | Now | Change | Rank in Illinois | |---|---|---|---|---| | Population (2020 → 2025) | 36,998 | 36,147 | ▼ 2.3% | 38th of 102 by size | | Total jobs (2019 → 2025) | 19,915 | 19,432 | ▼ 2.4% | 62nd of 102 by growth | | Average annual pay (2019 → 2025) | $44,016 | $59,848 | ▲ 36.0% | — | | Unemployment rate (2019 → August 2026) | 4.5% | 4.6% | ▲ 0.1pts | — | | Generating capacity added since 2019 | — | 2 MW | | — | | Generating capacity retired since 2019 | — | 0 MW | | — | | Planned generation (Aug 2026) | — | 155 MW | 7750% of today's fleet | 14th of 57 by size | Ameren Illinois Company is the largest utility serving Jefferson County, one of 3 with territory here. Its residential customers paid an average 15.26¢/kWh in 2024. Unemployment was 4.6% in August 2026, against 4.5% in 2019. 36,147 people live here, down 2.3% since 2020. ## Who powers Jefferson County ### Utilities with service territory in Jefferson County | Utility | Ownership | Service | Residential customers (systemwide) | Residential price, 2024 | Commercial share of sales | |---|---|---|---|---|---| | Ameren Illinois Company | Investor Owned | Bundled | 1,060,894 | 15.26¢ | 28% | | Tri-County Electric Coop, Inc (IL) | Cooperative | Bundled | 16,197 | 16.04¢ | 9% | | Wayne-White Counties Elec Coop | Cooperative | Bundled | 11,957 | 16.58¢ | 21% | Customer counts, prices and sales shares cover each utility's whole system in the state, not only this county. Commercial sales include data centers. ### Operating power plants | Technology | Capacity | Share | |---|---|---| | Solar | 2 MW | 100% | | Largest plants | Owner | Technology | MW | Since | |---|---|---|---|---| | Marlow Solar, LLC CSG | Marlow Solar, LLC | Solar | 2 MW | 2020 | ### Planned generation | Plant | Technology | MW | Status | Year | Owner | |---|---|---|---|---|---| | Casey Fork Solar, LLC | Solar Photovoltaic | 150 MW | Built, not yet operating | 2026 | RWE Clean Energy | | Harper Creek Solar, LLC | Solar Photovoltaic | 5 MW | Under construction (≤50%) | 2026 | Dimension Energy LLC | ## The Jefferson County labor market | Industry (2025) | Jobs | Average pay | Concentration vs U.S. | |---|---|---|---| | All industries | 19,432 | $59,848 | 1.00 | Concentration is the BLS location quotient: 1.0 means the industry holds the same share of local jobs as it does nationally. Industry rows count private employers; cells BLS suppresses are left out. ## Data centers and local rules in Jefferson County No data center, local measure or delayed project is on record in Jefferson County. Illinois has 28 local measures on record statewide. ## Jefferson County and its neighbors Of the 6 counties that border Jefferson County, Perry County carries the most build-out activity: data centers, planned generation and operating plants combined. [[[[[[ | County | Population | Jobs since 2019 | Operating MW | Planned MW | Data centers | Local measures | |---|---|---|---|---|---|---| | Jefferson County | 36,147 | ▼ 2.4% | 2 MW | 155 MW | — | — | | Franklin County](https://savrn.com/power-supply-chain-map/illinois/franklin-county) | 36,916 | ▲ 0.6% | 2 MW | — | — | — | | Hamilton County](https://savrn.com/power-supply-chain-map/illinois/hamilton-county) | 7,859 | ▲ 3.0% | 6 MW | — | — | — | | Marion County](https://savrn.com/power-supply-chain-map/illinois/marion-county) | 36,382 | ▼ 4.3% | 372 MW | — | — | — | | Perry County](https://savrn.com/power-supply-chain-map/illinois/perry-county) | 20,160 | ▼ 5.2% | 535 MW | 168 MW | — | — | | Washington County](https://savrn.com/power-supply-chain-map/illinois/washington-county) | 13,564 | ▼ 6.6% | 5 MW | — | — | — | | Wayne County](https://savrn.com/power-supply-chain-map/illinois/wayne-county) | 15,882 | ▲ 2.4% | — | — | — | — | ## More of Illinois [All Illinois countiesThe state power page and county mapOpen →](https://savrn.com/power-supply-chain-map/illinois)[Franklin County36,916 peopleOpen →](https://savrn.com/power-supply-chain-map/illinois/franklin-county)[Marion County36,382 peopleOpen →](https://savrn.com/power-supply-chain-map/illinois/marion-county)[Perry County20,160 peopleOpen →](https://savrn.com/power-supply-chain-map/illinois/perry-county)[Wayne County15,882 peopleOpen →](https://savrn.com/power-supply-chain-map/illinois/wayne-county)[Washington County13,564 peopleOpen →](https://savrn.com/power-supply-chain-map/illinois/washington-county) ## Jefferson County, answered from the record ### Who provides electricity in Jefferson County, Illinois? 3 utilities have service territory in Jefferson County in the EIA-861 2024 report: Ameren Illinois Company, Tri-County Electric Coop, Inc (IL), Wayne-White Counties Elec Coop. The largest, Ameren Illinois Company, charged residential customers 15.26¢/kWh on average in 2024. ### What county is Mount Vernon, IL in? Mount Vernon is in Jefferson County, Illinois. About 14,187 people live there (2025 Census estimate). ### What county is Mount Vernon Township, IL in? Mount Vernon Township is in Jefferson County, Illinois. About 12,192 people live there (2025 Census estimate). ### What power plants are in Jefferson County? 1 operating plant with 2 MW of capacity. The largest is Marlow Solar, LLC CSG (2 MW, solar). ### How much new power is planned in Jefferson County? 155 MW across 2 units in the August 2026 EIA-860M inventory, 155 MW of it under construction or built. The largest owner is RWE Clean Energy. ### Are there data centers in Jefferson County? The SAVRN Data Center Map has no data center in Jefferson County. ### Is Jefferson County adding jobs? Employers counted 19,432 jobs in 2025 against 19,915 in 2019 (-2.4%, BLS QCEW). ### Does Jefferson County have a data center moratorium? No county-level measure is on record for Jefferson County. Illinois has 28 local measures statewide, listed on the state page. --- Canonical: https://savrn.com/power-supply-chain-map/illinois/jefferson-county Updated: 2026-10-08. Refreshed weekly by SAVRN from EIA, BLS, BEA, Census and the SAVRN trackers. License: CC BY 4.0 (https://creativecommons.org/licenses/by/4.0/).