Marion County is a county in Illinois, United States, centred on the twin rail towns of Salem and Centralia in the south-central part of the state. It had a population of 37,729 at the 2020 census and covers 572 square miles (1,480 km2) of land centred near 38°39′N 88°55′W.
Salem is the county seat, and its postal code is 62881. The county holds four incorporated cities, ten villages, and a scatter of unincorporated hamlets spread across 17 townships. Marion County runs on Central time and carries FIPS code 17121.
Towns & Villages in Marion County
Marion County has 25 named places on record: four cities, ten villages, and eleven smaller unincorporated communities. Centralia is the largest city and straddles the Marion–Clinton county line; Salem, the county seat, sits at the junction of Interstates 57 and 64. Township assignment and current population figures are not available for every small unincorporated place, marked — below rather than guessed.
| Place | Type | Township | Pop. | ZIP |
|---|---|---|---|---|
| Salem | City · seat | Salem | — | 62881 |
| Centralia | City | Centralia | — | 62801 |
| Kinmundy | City | Kinmundy | — | 62854 |
| Wamac | City | — | — | — |
| Alma | Village | Alma | — | 62807 |
| Central City | Village | — | — | — |
| Iuka | Village | Iuka | — | 62849 |
| Junction City | Village | — | — | — |
| Kell | Village | — | — | 62853 |
| Odin | Village | Odin | — | 62870 |
| Patoka | Village | Patoka | — | 62875 |
| Sandoval | Village | Sandoval | — | 62882 |
| Vernon | Village | — | — | 62892 |
| Walnut Hill | Village | — | — | 62893 |
| Tonti | Unincorp. | Tonti | — | — |
| Omega | Unincorp. | Omega | — | — |
| Bannister | Unincorp. | — | — | — |
| Brubaker | Unincorp. | — | — | — |
| Cartter | Unincorp. | — | — | — |
| Fairman | Unincorp. | — | — | — |
| Foxville | Unincorp. | — | — | — |
| Helm | Unincorp. | — | — | — |
| Hickory Hill | Unincorp. | — | — | — |
| Hubbard Woods | Unincorp. | — | — | — |
| Lester | Unincorp. | — | — | — |
| Selmaville | Unincorp. | — | — | — |
| Union Town | Unincorp. | — | — | — |
Centralia is a split city: most of it lies in Marion County, but a slice of its southwest side crosses into Clinton County next door — both halves share the same city government and ZIP code.
Townships
Marion County has 17 civil townships. Confirmed 2020 township-level population counts were not available at the time of writing, so the Pop. column is left blank rather than estimated.
| Township | Pop. (2020) | Main settlements |
|---|---|---|
| Salem | — | Salem, Junction City |
| Centralia | — | Centralia, Central City, Wamac |
| Kinmundy | — | Kinmundy |
| Sandoval | — | Sandoval |
| Alma | — | Alma |
| Iuka | — | Iuka |
| Odin | — | Odin |
| Patoka | — | Patoka |
| Omega | — | Omega |
| Tonti | — | Tonti |
| Carrigan | — | — |
| Foster | — | — |
| Haines | — | Kell |
| Meacham | — | — |
| Raccoon | — | — |
| Romine | — | Vernon |
| Stevenson | — | Walnut Hill |
ZIP Codes
- 62801 — Centralia (also serves Central City and Wamac)
- 62807 — Alma
- 62849 — Iuka
- 62853 — Kell
- 62854 — Kinmundy
- 62870 — Odin
- 62875 — Patoka
- 62881 — Salem (also serves Junction City)
- 62882 — Sandoval
- 62892 — Vernon
- 62893 — Walnut Hill
Tonti and the county’s smaller unincorporated hamlets rely on the ZIP code of their nearest post-office town rather than one of their own.
Geography
Marion County sits on the gently rolling till plains typical of south-central Illinois. Of its 576 square miles, 572 square miles are land and 3.7 square miles (0.6%) are water. The county’s small streams feed west into the Kaskaskia River watershed. Marion County borders Fayette County to the north, Clay County to the east, Wayne County to the southeast, Jefferson County to the south, Washington County to the southwest, and Clinton County to the west.
Demographics
Marion County had 37,729 residents at the 2020 census, a density of about 66 people per square mile. Centralia and Salem are by far its two largest communities, together home to more than half the county’s population. Marion County’s median household income runs well below the Illinois median of $80,306, reflecting an economy still weighted toward manufacturing, agriculture, and health care rather than the state’s higher-wage metro sectors.
Economy & Local Life
Corn and soybean farming dominates the townships outside Centralia and Salem, while the two cities anchor the county’s retail, health care, and light-manufacturing base. Centralia grew up as a Illinois Central Railroad division point and later an oil and coal town; both industries left a lasting mark on its downtown and neighborhoods. Salem, a few miles south, is the county seat and home to Salem Township Hospital. Each August, Marion County’s fair and the Salem-based Marion County Fair draw much of the county together.
History
Marion County was organized on January 24, 1823, from parts of Jefferson and Fayette counties. It is named for General Francis Marion, the South Carolina militia leader nicknamed the “Swamp Fox” during the American Revolution. On March 25, 1947, an explosion at the Centralia Coal Company’s No. 5 mine just outside Centralia killed 111 miners, one of the deadliest mining disasters in Illinois history and a catalyst for later federal mine-safety reform.
Getting There
Interstate 57 crosses the county north–south and meets Interstate 64 at Salem; U.S. Routes 50 and 51 also run through the county.
- Salem — 65 miles east of St. Louis, Missouri
- Centralia — 8 miles north of Salem
- Mount Vernon — 20 miles south of Salem
- Effingham — 30 miles northeast of Salem
Amtrak’s City of New Orleans and Illini/Saluki trains stop at Centralia on the Chicago–New Orleans corridor. The nearest major commercial airport is St. Louis Lambert International Airport, roughly 70 miles west.
Frequently Asked Questions
Where is Marion County, Illinois?
It is in south-central Illinois, about 65 miles east of St. Louis, Missouri, along the Interstate 57/64 corridor.
What is the population of Marion County?
37,729 people at the 2020 census.
How big is Marion County?
572 square miles of land (1,480 km2), plus 3.7 square miles of water.
What is the county seat of Marion County?
Salem is the county seat.
How many towns are in Marion County?
Four cities (Salem, Centralia, Kinmundy, and Wamac), ten villages, and a number of smaller unincorporated communities.
What ZIP codes are in Marion County?
Eleven, led by 62881 (Salem) and 62801 (Centralia); see the ZIP Codes section above for the full list.
What happened at the Centralia mine disaster?
An explosion at the No. 5 mine on March 25, 1947, killed 111 miners and is remembered as one of Illinois’s worst mining tragedies.
More counties in this state: Towns and villages in Illinois.