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County · code 17087

Johnson CountyIllinois

Johnson County is a county in southern Illinois with its seat in Vienna. It was created on September 14, 1812, from Randolph and Gallatin counties and is named after Richard Mentor Johnson.

  • Founded1812
  • County seatVienna
  • Named forRichard Mentor Johnson
  • Land area344 sq mi + 5 sq mi water
  • Population13,308 2020 Census
  • Parcels mapped12,995 checked 14 October 2026
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Updated

WilliamsonMassacPopePulaskiUnion Vienna Census outline · seat marked

Where it is

Johnson on the map of Illinois

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

Adams CountyAlexander CountyBond CountyBoone CountyBrown CountyBureau CountyCalhoun CountyCarroll CountyCass CountyChampaign CountyChristian CountyClark CountyClay CountyClinton CountyColes CountyCook CountyCrawford CountyCumberland CountyDeKalb CountyDe Witt CountyDouglas CountyDuPage CountyEdgar CountyEdwards CountyEffingham CountyFayette CountyFord CountyFranklin CountyFulton CountyGallatin CountyGreene CountyGrundy CountyHamilton CountyHancock CountyHardin CountyHenderson CountyHenry CountyIroquois CountyJackson CountyJasper CountyJefferson CountyJersey CountyJo Daviess CountyKane CountyKankakee CountyKendall CountyKnox CountyLake CountyLaSalle CountyLawrence CountyLee CountyLivingston CountyLogan CountyMcDonough CountyMcHenry CountyMcLean CountyMacon CountyMacoupin CountyMadison CountyMarion CountyMarshall CountyMason CountyMassac CountyMenard CountyMercer CountyMonroe CountyMontgomery CountyMorgan CountyMoultrie CountyOgle CountyPeoria CountyPerry CountyPiatt CountyPike CountyPope CountyPulaski CountyPutnam CountyRandolph CountyRichland CountyRock Island CountySt. Clair CountySaline CountySangamon CountySchuyler CountyScott CountyShelby CountyStark CountyStephenson CountyTazewell CountyUnion CountyVermilion CountyWabash CountyWarren CountyWashington CountyWayne CountyWhite CountyWhiteside CountyWill CountyWilliamson CountyWinnebago CountyWoodford CountyJohnson County Johnson
Counties of Illinois · Johnson highlighted

History

Formed in 1812 from Randolph County and Gallatin County

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

Johnson County was created by the Illinois Territory from Randolph and Gallatin counties in 1812. It lost land to the creation of Jackson and Pope counties in 1816, then gained from Pope while losing to the creation of Franklin and Union counties in 1818. When Illinois became a state from the Illinois Territory on December 3, 1818, Johnson became a county within the state. The county lost more territory to the creation of Massac County in 1843.

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

  1. 1812
    Johnson County created Johnson created by Illinois Territory from Randolph; boundary with Gallatin is estimated.
    from Randolphfrom Gallatin
    · Ill. Terr. Recs., 26; Terr. Papers U.S., 17:643
  2. 1816
    Lost territory Johnson lost to creation of Jackson and Pope.
    to Jacksonto Pope
    · Ill. Terr. Laws, 215-219; Ill. Laws 1822-1823, pp. 122-123
  3. 1818
    Gained territory Johnson gained from Pope, lost to creation of Franklin and Union, and lost to creation of Non-County Area 1.
    from Popefrom Franklinfrom Union
    · Ill. Terr. Laws, 290-294
  4. 1818
    Became part of Illinois Johnson became a county in the state of Illinois when Illinois was created from Illinois Territory. · Terr. Papers U.S., 10:803; U.S. Stat., vol. 3, ch. 67 [1818], secs. 1-2, 7/pp. 428-429, 431, and res. 1 [1818]/p. 536
  5. 1843
    Lost territory Johnson lost to creation of Massac.
    to Massac
    · Ill. Laws 1842-1843, pp. 74-76

Land and parcels

What the maps cover in Johnson

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

Johnson by the Census

Population
13,308 2020 Census count
Housing units
5,526 2020 Census count
Land area
344 square miles
Water area
5 square miles
People per sq mi
39 population ÷ land area

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

See your own lot on these maps

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Questions

Common questions about Johnson County

When was Johnson County founded?
Johnson County was founded in 1812, formed from Randolph County and Gallatin County, and named after Richard Mentor Johnson.
What is the county seat of Johnson County?
The county seat of Johnson County is Vienna.
Is there an online parcel map for Johnson County?
Yes. Johnson County publishes a parcel map of 12,995 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Johnson County's boundary or name changed?
Johnson County was created in 1812 from Randolph County and Gallatin County. Since then the Atlas of Historical County Boundaries records 4 later changes, chiefly involving Pope County, Franklin County and Jackson County.
Is my lot in a flood zone?
We do not have flood maps for Johnson 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