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County · code 17121

Marion CountyIllinois

Marion County is a county in Illinois, with its seat in Salem. It was created in 1823 and named after Francis Marion.

  • Founded1823
  • County seatSalem
  • Named forFrancis Marion
  • Land area573 sq mi + 3.6 sq mi water
  • Population37,729 2020 Census
  • Parcels mapped33,867 checked 15 October 2026
Open the free map Click any parcel in Marion County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

JeffersonFayetteClintonWayne Salem Census outline · seat marked

Where it is

Marion on the map of Illinois

Illinois has 102 counties and county equivalents, each with its own records office. Shapes with a page are links.

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Counties of Illinois · Marion highlighted

History

Formed in 1823 from Fayette County and Jefferson County

An old deed may name a county that no longer exists, or a boundary that has since moved.

Marion County was created on January 24, 1823, from Fayette County and Jefferson County.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries.

  1. 1823
    Marion County created Marion created from Fayette and Jefferson.
    from Fayettefrom Jefferson
    · Ill. Laws 1822-1823, pp. 49-50

Land and parcels

What the maps cover in Marion

Who publishes each layer, how good it is, and when we last checked.

Official
from the office that keeps the record
Good enough
a reliable statewide or national copy
Fallback
a guide only; check the official record
Missing
nothing public found yet

People and land

Marion by the Census

Population
37,729 2020 Census count
Housing units
17,358 2020 Census count
Land area
573 square miles
Water area
3.6 square miles
People per sq mi
66 population ÷ land area

Source: US Census Bureau, 2020 Census; US Census Bureau, 2020 Gazetteer Files. Not endorsed or certified by the Census Bureau.

Rules and offices

Marion County's official site

We have found the county's site but not its offices yet; start there.

County government

See your own lot on these maps

Open Marion County on Parcel Chart's free map and click your parcel. Save it with a free account; the full record of your place (site map, projects, documents) is Pro, in early access.

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Questions

Common questions about Marion County

When was Marion County founded?
Marion County was founded in 1823, formed from Fayette County and Jefferson County, and named after Francis Marion.
What is the county seat of Marion County?
The county seat of Marion County is Salem.
Is there an online parcel map for Marion County?
Yes. A public source publishes a parcel map of 33,867 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Marion County's boundary or name changed?
Marion County was created in 1823 from Fayette County and Jefferson County. The Atlas of Historical County Boundaries records no boundary change since.
Is my lot in a flood zone?
We do not have flood maps for Marion County yet. Look up the address on FEMA's Flood Map Service Center, which shows the effective flood map for any lot.

Nearby

Counties next door