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County · code 29185

St. Clair CountyMissouri

St. Clair County is a county in Missouri, with its seat in Osceola. It was created on January 16, 1833, from Lafayette County.

  • Founded1833
  • County seatOsceola
  • Named forArthur St. Clair
  • Land area675 sq mi + 27 sq mi water
  • Population9,284 2020 Census
  • Parcels mapped10,992 checked 14 October 2026
Open the free map Click any parcel in St. Clair County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

CedarHenryHickoryBentonPolkVernonBates Osceola Census outline · seat marked

Where it is

St. Clair on the map of Missouri

Missouri has 115 counties and county equivalents, each with its own records office. Shapes with a page are links.

Adair CountyAndrew CountyAtchison CountyAudrain CountyBarry CountyBarton CountyBates CountyBenton CountyBollinger CountyBoone CountyBuchanan CountyButler CountyCaldwell CountyCallaway CountyCamden CountyCape Girardeau CountyCarroll CountyCarter CountyCass CountyCedar CountyChariton CountyChristian CountyClark CountyClay CountyClinton CountyCole CountyCooper CountyCrawford CountyDade CountyDallas CountyDaviess CountyDeKalb CountyDent CountyDouglas CountyDunklin CountyFranklin CountyGasconade CountyGentry CountyGreene CountyGrundy CountyHarrison CountyHenry CountyHickory CountyHolt CountyHoward CountyHowell CountyIron CountyJackson CountyJasper CountyJefferson CountyJohnson CountyKnox CountyLaclede CountyLafayette CountyLawrence CountyLewis CountyLincoln CountyLinn CountyLivingston CountyMcDonald CountyMacon CountyMadison CountyMaries CountyMarion CountyMercer CountyMiller CountyMississippi CountyMoniteau CountyMonroe CountyMontgomery CountyMorgan CountyNew Madrid CountyNewton CountyNodaway CountyOregon CountyOsage CountyOzark CountyPemiscot CountyPerry CountyPettis CountyPhelps CountyPike CountyPlatte CountyPolk CountyPulaski CountyPutnam CountyRalls CountyRandolph CountyRay CountyReynolds CountyRipley CountySt. Charles CountySte. Genevieve CountySt. Francois CountySt. Louis CountySaline CountySchuyler CountyScotland CountyScott CountyShannon CountyShelby CountyStoddard CountyStone CountySullivan CountyTaney CountyTexas CountyVernon CountyWarren CountyWashington CountyWayne CountyWebster CountyWorth CountyWright CountySt. Louis citySt. Clair County St. Clair
Counties of Missouri · St. Clair highlighted

History

Formed in 1833 from Lafayette County and Greene County

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

St. Clair County was named after Arthur St. Clair. When first created in 1833, it was not fully organized and was attached to Greene County for civil and military purposes, later being attached to Henry County before becoming fully organized in 1841.

Boundary changes from the Newberry Library, Atlas of Historical County Boundaries; the 5 that matter most are shown first.

  1. 1833
    St. Clair County created St. Clair created from Lafayette, Non-County Area 15, and Non-County Area 16; St. Clair not fully organized, attached to Greene "for all civil and military purposes."
    from Lafayettefrom Greene
    · Mo. Laws 1832-1833, pub., ch. 27, sec. 4/p. 51
  2. 1833
    Lost territory St. Clair lost to creation of Pettis.
    to Pettis
    · Mo. Laws 1832-1833, pub., ch. 30, sec. 1/pp. 53-54
  3. 1835
    Gained territory St. Clair gained from Non-County Area 20, lost to creation of Benton. Non-County Area 20 eliminated.
    from Benton
    · Mo. Laws 1834-1835, priv. and loc., pp. 41-42
  4. 1835
    Lost territory St. Clair lost to creation of Polk.
    to Polk
    · Mo. Laws 1834-1835, priv. and loc., pp. 42-43
  5. 1835
    Lost territory St. Clair lost to Polk.
    to Polk
    · Mo. Laws 1834-1835, priv. and loc., p. 44
Show all 11 changes (6 more)
  1. 1833
    St. Clair County created St. Clair created from Lafayette, Non-County Area 15, and Non-County Area 16; St. Clair not fully organized, attached to Greene "for all civil and military purposes."
    from Lafayettefrom Greene
    · Mo. Laws 1832-1833, pub., ch. 27, sec. 4/p. 51
  2. 1833
    Lost territory St. Clair lost to creation of Pettis.
    to Pettis
    · Mo. Laws 1832-1833, pub., ch. 30, sec. 1/pp. 53-54
  3. 1835
    Gained territory St. Clair gained from Non-County Area 20, lost to creation of Benton. Non-County Area 20 eliminated.
    from Benton
    · Mo. Laws 1834-1835, priv. and loc., pp. 41-42
  4. 1835
    Lost territory St. Clair lost to creation of Polk.
    to Polk
    · Mo. Laws 1834-1835, priv. and loc., pp. 42-43
  5. 1835
    Changed St. Clair detached from Greene, attached to Rives (now Henry) "for all civil and military purposes."
    GreeneRivesHenry
    · Mo. Laws 1843-1835, priv. and loc., p. 47
  6. 1835
    Lost territory St. Clair lost to Polk.
    to Polk
    · Mo. Laws 1834-1835, priv. and loc., p. 44
  7. 1841
    Gained territory St. Clair gained from Non-County Area 32; Non-County Area 32 eliminated. St. Clair fully organized, detached from Rives (now Henry).
    from Rivesfrom Henry
    · Mo. Laws 1840-1841, pub., secs, 25-27/p. 35
  8. 1845
    Lost territory St. Clair lost to creation of Cedar.
    to Cedar
    · Mo. Laws 1844-1845, secs. 49-51/p. 37
  9. 1845
    Gained territory St. Clair gained from Polk.
    from Polk
    · Mo. Laws 1844-1845, loc. and priv., p. 47
  10. 1859
    Gained territory St. Clair gained from Henry.
    from Henry
    · Mo. Laws 1858-1859, p. 425
  11. 1879
    Gained territory St. Clair gained from Benton (the area gained by St. Clair was incorrectly included as part of Benton in the state's Revised Statutes until 1939).
    from Benton
    · Mo. Laws 1889, p. 66; Mo. Laws 1939, pp. 635-636, 653-654; Mo. Vernon's 1949, pp. 13-14

Land and parcels

What the maps cover in St. Clair

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

St. Clair by the Census

Population
9,284 2020 Census count
Housing units
5,288 2020 Census count
Land area
675 square miles
Water area
27 square miles
People per sq mi
14 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

St. Clair 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

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Questions

Common questions about St. Clair County

When was St. Clair County founded?
St. Clair County was founded in 1833, formed from Lafayette County and Greene County, and named after Arthur St. Clair.
What is the county seat of St. Clair County?
The county seat of St. Clair County is Osceola.
Is there an online parcel map for St. Clair County?
Yes. St. Clair County publishes a parcel map of 10,992 parcels, rated good enough here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has St. Clair County's boundary or name changed?
St. Clair County was created in 1833 from Lafayette County and Greene County. Since then the Atlas of Historical County Boundaries records 10 later changes, chiefly involving Henry County, Polk County and Benton County.
Is my lot in a flood zone?
We do not have flood maps for St. Clair 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