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County · code 19183

Washington CountyIowa

Washington County is a county in Iowa, with its seat in Washington. It was formed on January 18, 1838, from Henry, Louisa, and Muscatine counties and named after George Washington.

  • Founded1838
  • County seatWashington
  • Named forGeorge Washington
  • Land area569 sq mi + 2.1 sq mi water
  • Population22,565 2020 Census
  • Parcels mapped21,609 checked 15 October 2026
Open the free map Click any parcel in Washington County: acreage, parcel id, address and who publishes the map. No sign-in.

Updated

JohnsonJeffersonKeokukLouisa Washington Census outline · seat marked

Where it is

Washington 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 CountyO'Brien CountyOsceola CountyPage CountyPalo Alto CountyPlymouth CountyPocahontas CountyPolk CountyPottawattamie CountyPoweshiek CountyRinggold CountySac CountyScott CountyShelby CountySioux CountyStory CountyTama CountyTaylor CountyUnion CountyVan Buren CountyWapello CountyWarren CountyWayne CountyWebster CountyWinnebago CountyWinneshiek CountyWoodbury CountyWorth CountyWright CountyWashington County Washington
Counties of Iowa · Washington highlighted

History

Formed in 1838 from Henry County, Louisa County and Muscatine County

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

Originally created by Wisconsin Territory as Slaughter County from Henry, Louisa, and Muscatine counties, it became part of Iowa Territory on July 3, 1838. On January 25, 1839, Slaughter County was renamed Washington and gained territory from Johnson and Keokuk counties. Washington became an Iowa county when the state of Iowa was created from Iowa Territory on December 28, 1846.

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

  1. 1838
    Washington County created Slaughter (now Washington) created by Wisconsin Territory from Henry, Louisa, Muscatine, and Non-County Area 1; Non-County Area 3 attached to Slaughter "for judicial purposes."
    from Henryfrom Louisafrom Muscatine
    · Wis. Terr. Laws 1837, no. 67, secs. 1-7/pp. 381-384
  2. 1838
    Became part of Iowa Slaughter (now Washington) became an Iowa Territory county when Iowa Territory was created from Wisconsin Territory. · U.S. Stat., vol. 5, ch. 96[1838]/pp. 235-241
  3. 1839
    Renamed Slaughter renamed Washington; Washington gained from Johnson, Keokuk, and Non-County Area 3 attached to Slaughter.
    formerly Slaughter
    · Iowa Terr. Laws 1838-1839, pp. 100-101
  4. 1845
    Lost territory Washington lost to Johnson.
    to Johnson
    · Iowa Terr. Laws 1845, ch. 45, sec. 1/pp. 66-67
  5. 1846
    Became part of Iowa Washington became an Iowa county when the state of Iowa was created from Iowa Territory. · U.S. Stat., vol. 9, ch. 1[1847]/p. 117
Show all 8 changes (3 more)
  1. 1838
    Washington County created Slaughter (now Washington) created by Wisconsin Territory from Henry, Louisa, Muscatine, and Non-County Area 1; Non-County Area 3 attached to Slaughter "for judicial purposes."
    from Henryfrom Louisafrom Muscatine
    · Wis. Terr. Laws 1837, no. 67, secs. 1-7/pp. 381-384
  2. 1838
    Became part of Iowa Slaughter (now Washington) became an Iowa Territory county when Iowa Territory was created from Wisconsin Territory. · U.S. Stat., vol. 5, ch. 96[1838]/pp. 235-241
  3. 1839
    Lost territory Slaughter (now Washington) lost to Louisa.
    to Louisa
    · Iowa Terr. Laws 1838-1839, pp. 89-91
  4. 1839
    Renamed Slaughter renamed Washington; Washington gained from Johnson, Keokuk, and Non-County Area 3 attached to Slaughter.
    formerly Slaughter
    · Iowa Terr. Laws 1838-1839, pp. 100-101
  5. 1843
    Changed Keokuk detached from Johnson, attached to Washington; Mahaska attached to Washington. All attachments were "for judicial, revenue, and election purposes."
    KeokukJohnsonMahaska
    · Iowa Terr. Rev. Stat. 1843, ch. 34, secs. 5-6/pp. 132-133
  6. 1844
    Changed Keokuk and Mahaska fully organized, detached from Washington; Non-County Area 3 detached from Washington, attached to Mahaska "for election, revenue, and judicial purposes".
    KeokukMahaska
    · Iowa Terr. Laws 1843-1844, ch. 68, secs.1, 17-18/pp. 85-89
  7. 1845
    Lost territory Washington lost to Johnson.
    to Johnson
    · Iowa Terr. Laws 1845, ch. 45, sec. 1/pp. 66-67
  8. 1846
    Became part of Iowa Washington became an Iowa county when the state of Iowa was created from Iowa Territory. · U.S. Stat., vol. 9, ch. 1[1847]/p. 117

Land and parcels

What the maps cover in Washington

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

Washington by the Census

Population
22,565 2020 Census count
Housing units
9,573 2020 Census count
Land area
569 square miles
Water area
2.1 square miles
People per sq mi
40 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 Washington 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 Washington County

When was Washington County founded?
Washington County was founded in 1838, formed from Henry County, Louisa County and Muscatine County, and named after George Washington.
What is the county seat of Washington County?
The county seat of Washington County is Washington.
Is there an online parcel map for Washington County?
Yes. Iowa Department of Homeland Security and Emergency Management (statewide parcels, mirrored by the University of Iowa) publishes a parcel map of 21,609 parcels, rated fallback here. You can click any parcel on it in Parcel Chart's free map, no sign-in needed.
Has Washington County's boundary or name changed?
Washington County was created in 1838 from Henry County, Louisa County and Muscatine County. Since then the Atlas of Historical County Boundaries records 7 later changes, chiefly involving Johnson County, Keokuk County and Mahaska County. It was formerly called Slaughter.
Is my lot in a flood zone?
We do not have flood maps for Washington 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