Parcel Chartplaces Open the free map

County · code 17133

Monroe CountyIllinois

Monroe County is a county in Illinois, on the border with Missouri, founded in 1816, with its seat at Waterloo.

  • Founded1816
  • County seatWaterloo
  • Named forJames Monroe
  • Land area385 sq mi + 13 sq mi water
  • Population34,962 2020 Census
  • Parcels mapped19,623 checked 15 October 2026
Open the free map Click any parcel in Monroe County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

St. ClairJefferson, MOSte. Genevieve, MORandolphSt. Louis, MO Waterloo Census outline · seat marked

Where it is

Monroe 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 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 CountyMonroe County Monroe
Counties of Illinois · Monroe highlighted

History

Formed in 1816 from Randolph County and St. Clair County

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

Monroe County was created on June 1, 1816, by the Illinois Territory from Randolph County and St. Clair County. When Illinois became a state on December 3, 1818, Monroe County became a county in the state of Illinois. The county gained additional territory from St. Clair County in 1825 and again in 1827.

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

  1. 1816
    Monroe County created Monroe created by Illinois Territory from Randolph and St. Clair.
    from Randolphfrom St. Clair
    · Ill. Terr. Laws, 195-198
  2. 1818
    Became part of Illinois Monroe 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. 1825
    Gained territory Monroe gained from St. Clair.
    from St. Clair
    · Ill. Laws 1824-1825, pp. 109-110
  4. 1827
    Gained territory Monroe gained from St. Clair.
    from St. Clair
    · Ill. Laws 1826-1827, pp. 7-8
  5. 1829
    Boundary clarified Boundary between Monroe and Randolph was clarified (no change).
    with Randolphno change
    · Ill. Rev. Code 1828-1829, pp. 31-32

Land and parcels

What the maps cover in Monroe

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

Monroe by the Census

Population
34,962 2020 Census count
Housing units
14,540 2020 Census count
Land area
385 square miles
Water area
13 square miles
People per sq mi
91 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 Monroe 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.

Open the free map no sign-in Pro early access

Questions

Common questions about Monroe County

When was Monroe County founded?
Monroe County was founded in 1816, formed from Randolph County and St. Clair County, and named after James Monroe.
What is the county seat of Monroe County?
The county seat of Monroe County is Waterloo.
Is there an online parcel map for Monroe County?
Yes. A public source publishes a parcel map of 19,623 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Monroe County's boundary or name changed?
Monroe County was created in 1816 from Randolph County and St. Clair County. Since then the Atlas of Historical County Boundaries records 3 later changes, chiefly involving St. Clair County.
Is my lot in a flood zone?
We do not have flood maps for Monroe 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