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County · code 19141

O'Brien CountyIowa

O'Brien County is a county in Iowa with its seat in Primghar, formed in 1851.

  • Founded1851
  • County seatPrimghar
  • Named forWilliam Smith O'Brien
  • Land area573 sq mi + 0.2 sq mi water
  • Population14,182 2020 Census
  • Parcels mapped18,266 checked 15 October 2026
Open the free map Click any parcel in O'Brien County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

OsceolaCherokeeClaySioux Primghar Census outline · seat marked

Where it is

O'Brien on the map of Iowa

Iowa has 99 counties and county equivalents, each with its own records office. Shapes with a page are links.

Adair CountyAdams CountyAllamakee CountyAppanoose CountyAudubon CountyBenton CountyBlack Hawk CountyBoone CountyBremer CountyBuchanan CountyBuena Vista CountyButler CountyCalhoun CountyCarroll CountyCass CountyCedar CountyCerro Gordo CountyCherokee CountyChickasaw CountyClarke CountyClay CountyClayton CountyClinton CountyCrawford CountyDallas CountyDavis CountyDecatur CountyDelaware CountyDes Moines CountyDickinson CountyDubuque CountyEmmet CountyFayette CountyFloyd CountyFranklin CountyFremont CountyGreene CountyGrundy CountyGuthrie CountyHamilton CountyHancock CountyHardin CountyHarrison CountyHenry CountyHoward CountyHumboldt CountyIda CountyIowa CountyJackson CountyJasper CountyJefferson CountyJohnson CountyJones CountyKeokuk CountyKossuth CountyLee CountyLinn CountyLouisa CountyLucas CountyLyon CountyMadison CountyMahaska CountyMarion CountyMarshall CountyMills CountyMitchell CountyMonona CountyMonroe CountyMontgomery CountyMuscatine CountyOsceola CountyPage CountyPalo Alto CountyPlymouth CountyPocahontas CountyPolk CountyPottawattamie CountyPoweshiek CountyRinggold CountySac CountyScott CountyShelby CountySioux CountyStory CountyTama CountyTaylor CountyUnion CountyVan Buren CountyWapello CountyWarren CountyWashington CountyWayne CountyWebster CountyWinnebago CountyWinneshiek CountyWoodbury CountyWorth CountyWright CountyO'Brien County O'Brien
Counties of Iowa · O'Brien highlighted

History

Formed in 1851 from Polk County

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

O'Brien County was created from Non-County Area 9 attached to Polk County on January 15, 1851, but was not fully organized at that time. The county was named after William Smith O'Brien. O'Brien was attached to Woodbury County in 1853 for revenue, election, and judicial purposes, then fully organized and detached from Woodbury on April 7, 1860. The county had various judicial attachments to Clay and Cherokee counties in the 1860s before being fully organized and detached from Cherokee on February 10, 1870.

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

  1. 1851
    O'Brien County created O'Brien created from Non-County Area 9 attached to Polk; O'Brien not fully organized, not attached.
    from Polk
    · Iowa Acts 1850-1851, ch. 9, sec. 40/p. 36
  2. 1853
    Changed O'Brien attached to Woodbury "for revenue, election, and judicial purposes".
    Woodbury
    · Iowa Acts 1852-1853, ch. 8, sec. 14/p. 24
  3. 1860
    Changed O'Brien fully organized, detached from Woodbury.
    Woodbury
    · Swisher, "Organization of Counties," 575
  4. 1864
    Changed O'Brien attached to Clay "for judicial purposes."
    Clay
    · Iowa Acts 1864, ch. 47, secs. 2, 9/pp. 47-49
  5. 1868
    Changed O'Brien detached from Clay, attached to Cherokee "for judicial purposes".
    ClayCherokee
    · Iowa Acts 1868, ch. 73, secs. 2, 8/pp. 99-100
  6. 1870
    Changed O'Brien fully organized, detached from Cherokee when judicial attachments of 7 April 1868 were repealed.
    Cherokee
    · Iowa Acts 1870, ch. 2, secs. 3-4/pp. 3-4

Land and parcels

What the maps cover in O'Brien

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

O'Brien by the Census

Population
14,182 2020 Census count
Housing units
6,524 2020 Census count
Land area
573 square miles
Water area
0.2 square miles
People per sq mi
25 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

O'Brien 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

Open O'Brien 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 O'Brien County

When was O'Brien County founded?
O'Brien County was founded in 1851, formed from Polk County, and named after William Smith O'Brien.
What is the county seat of O'Brien County?
The county seat of O'Brien County is Primghar.
Is there an online parcel map for O'Brien County?
Yes. Iowa Department of Homeland Security and Emergency Management (statewide parcels, mirrored by the University of Iowa) publishes a parcel map of 18,266 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has O'Brien County's boundary or name changed?
O'Brien County was created in 1851 from Polk County. Since then the Atlas of Historical County Boundaries records 5 later changes, chiefly involving Cherokee County, Clay County and Woodbury County.
Is my lot in a flood zone?
We do not have flood maps for O'Brien 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