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County · code 17125

Mason CountyIllinois

Mason County is a county in Illinois with its county seat in Havana, formed in 1841.

  • Founded1841
  • County seatHavana
  • Named forGeorge Mason
  • Land area539 sq mi + 24 sq mi water
  • Population13,086 2020 Census
  • Parcels mapped16,643 checked 15 October 2026
Open the free map Click any parcel in Mason County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

MenardFultonCassTazewellLoganSchuyler Havana Census outline · seat marked

Where it is

Mason 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 · Mason highlighted

History

Formed in 1841 from Menard County and Tazewell County

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

Mason County was created on January 20, 1841, from parts of Menard and Tazewell counties. The county was named after George Mason.

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

  1. 1841
    Mason County created Mason created from Menard and Tazewell.
    from Menardfrom Tazewell
    · Ill. Laws 1840-1841, pp. 69-71

Land and parcels

What the maps cover in Mason

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

Mason by the Census

Population
13,086 2020 Census count
Housing units
6,626 2020 Census count
Land area
539 square miles
Water area
24 square miles
People per sq mi
24 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

Mason 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 Mason 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 Mason County

When was Mason County founded?
Mason County was founded in 1841, formed from Menard County and Tazewell County, and named after George Mason.
What is the county seat of Mason County?
The county seat of Mason County is Havana.
Is there an online parcel map for Mason County?
Yes. Mason County publishes a parcel map of 16,643 parcels, rated official here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Mason County's boundary or name changed?
Mason County was created in 1841 from Menard County and Tazewell 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 Mason 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