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County · code 17181

Union CountyIllinois

Union County is a county in Illinois, with its seat in Jonesboro. It was created on January 2, 1818.

  • Founded1818
  • County seatJonesboro
  • Named forUnited States
  • Land area413 sq mi + 8.7 sq mi water
  • Population17,244 2020 Census
  • Parcels mapped12,741 checked 14 October 2026
Open the free map Click any parcel in Union County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

PulaskiAlexanderJacksonJohnsonCape Girardeau, MOPerry, MO Jonesboro Census outline · seat marked

Where it is

Union 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 CountyJohnson 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 CountyVermilion CountyWabash CountyWarren CountyWashington CountyWayne CountyWhite CountyWhiteside CountyWill CountyWilliamson CountyWinnebago CountyWoodford CountyUnion County Union
Counties of Illinois · Union highlighted

History

Formed in 1818 from Johnson County

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

Union County was created by the Illinois Territory from Johnson County, with part of Johnson County attached to Union for administrative and judicial purposes. When Illinois became a state later that year, Union became a county in the state of Illinois. In 1819, the attached territory was lost when Alexander County was created.

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

  1. 1818
    Union County created Union created by Illinois Territory from Johnson; part of Johnson became Non-County Area 1 and was attached to Union for administrative and judicial purposes.
    from Johnson
    · Ill. Terr. Laws, 292-294
  2. 1818
    Became part of Illinois Union 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
  3. 1819
    Lost territory Non-County Area 1 attached to Union lost all territory to creation of Alexander; Non-County Area 1 eliminated.
    to Alexander
    · Ill. Laws 1819, pp. 113-114

Land and parcels

What the maps cover in Union

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

Union by the Census

Population
17,244 2020 Census count
Housing units
7,841 2020 Census count
Land area
413 square miles
Water area
8.7 square miles
People per sq mi
42 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

Who to ask before you build, dig or sell

Official county pages only. We link to them; we do not copy them, because they change.

Inside a city or town, permits usually come from that city rather than the county.

Permits

Zoning and code

County government

See your own lot on these maps

Open Union 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 Union County

When was Union County founded?
Union County was founded in 1818, formed from Johnson County, and named after United States.
What is the county seat of Union County?
The county seat of Union County is Jonesboro.
Is there an online parcel map for Union County?
Yes. Union County publishes a parcel map of 12,741 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Union County's boundary or name changed?
Union County was created in 1818 from Johnson County. Since then the Atlas of Historical County Boundaries records 2 later changes, chiefly involving Alexander County.
Who issues building permits in Union County?
The county's page on building permits: Permits – Union County Illinois. Inside a city or town, ask that city first.
Is my lot in a flood zone?
We do not have flood maps for Union 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