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County · code 17187

Warren CountyIllinois

Warren County is a county in Illinois with its seat in Monmouth. It was established in 1825 and covers 542.4 square miles.

  • Founded1825
  • County seatMonmouth
  • Named forJoseph Warren
  • Land area542 sq mi + 0.7 sq mi water
  • Population16,835 2020 Census
  • Parcels mapped14,136 checked 16 October 2026
Open the free map Click any parcel in Warren County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

HendersonMercerMcDonough Monmouth Census outline · seat marked

Where it is

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

History

Formed in 1825 from Pike County and Schuyler County

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

Warren County was created from Pike and Schuyler counties in 1825, and named after Joseph Warren. It was initially attached to Schuyler County for administrative purposes, then attached to Peoria County in 1826 before becoming fully organized in 1831. Mercer County was temporarily attached to Warren for judicial purposes in 1831 but became fully organized and detached in 1835, and Henderson County was created from Warren in 1841.

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

  1. 1825
    Warren County created Warren created from Non-County Area 3 attached to Pike; Warren not fully organized, attached to Schuyler "for all county purposes."
    from Pikefrom Schuyler
    · Ill. Laws 1824-1825, pp. 85-87, 92-96
  2. 1826
    Changed Warren detached from Schuyler, attached to Peoria "for county purposes."
    SchuylerPeoria
    · Ill. Laws 1826, pp. 76-77
  3. 1831
    Changed Warren fully organized, detached from Peoria. Mercer detached from Peoria, attached to Warren "for all judicial and other purposes."
    PeoriaMercer
    · Ill. Laws 1830-1831, pp. 67-68
  4. 1835
    Changed Mercer fully organized, detached from Warren.
    Mercer
    · Ill. Laws 1835-1835, p. 156
  5. 1837
    Changed Warren boundaries were extended to the middle of the Mississippi River. · Ill. Laws 1836-1837, pp. 91-92
  6. 1841
    Lost territory Warren lost to creation of Henderson.
    to Henderson
    · Ill. Laws 1840-1841, pp. 67-69

Land and parcels

What the maps cover in Warren

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

Warren by the Census

Population
16,835 2020 Census count
Housing units
7,602 2020 Census count
Land area
542 square miles
Water area
0.7 square miles
People per sq mi
31 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.

Zoning and code

County government

See your own lot on these maps

Open Warren 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 Warren County

When was Warren County founded?
Warren County was founded in 1825, formed from Pike County and Schuyler County, and named after Joseph Warren.
What is the county seat of Warren County?
The county seat of Warren County is Monmouth.
Is there an online parcel map for Warren County?
Yes. A public source publishes a parcel map of 14,136 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Warren County's boundary or name changed?
Warren County was created in 1825 from Pike County and Schuyler County. Since then the Atlas of Historical County Boundaries records 5 later changes, chiefly involving Mercer County, Peoria County and Henderson County.
Is my lot in a flood zone?
We do not have flood maps for Warren 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