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Iowa County Formation Table

County Formation

Wisconsin Territory was organized in 1836 from land formerly belonging to Michigan Territory encompassing the area as follows: south and east by Missouri, Illinois and Lake Michigan; east and north by Michigan, Lake Superior, and the International Line; westerly by the White Earth River and the Missouri River. In 1838 Wisconsin Territory was contracted to approximately the area of the present state, and the remainder of the territory was organized as Iowa Territory. In 1846 Iowa was admitted as a state, with its present boundaries. The remainder of the territory, being the residue of the original Wisconsin Territory, was unattached until the creation of Minnesota Territory in 1849.


The following table summarizes the formation dates of Iowa Counties. Note that counties have a complex history that this table does not adequately represent. For more detailed information, see the individual county website or consult the Histories of Iowa Counties at the State Library of Iowa.

Name Created Created from County seat Iowa County Home Page
Adair 1851 Cass Greenfield iagenweb.org/adair
Adams 1851 Taylor Corning iagenweb.org/adams
Allamakee 1847 Clayton Waukon iagenweb.org/allamakee
Appanoose 1843 Davis Centerville iagenweb.org/appanoose
Audubon 1851 Cass, Black Hawk Audubon iagenweb.org/audubon
Bancroft 1851 extinct    
Benton 1837 Indian Land Purchase; Wisconsin Territory Vinton iagenweb.org/benton
Black Hawk 1843 Delaware Waterloo iagenweb.org/blackhawk
Boone 1846 Polk Boone iagenweb.org/boone
Bremer 1851 Winnebago, Indian Reserve Waverly iagenweb.org/bremer
Buchanan 1837 Delaware, Wisconsin Territory Independence iagenweb.org/buchanan
Buncombe   changed to Lyon,1862    
Buena Vista 1851 Sac, Clay Storm Lake iagenweb.org/buenavista
Butler 1851 Buchanan, Black Hawk Allison iagenweb.org/butler
Calhoun 1855 formerly called Fox Rockwell City iagenweb.org/calhoun
Carroll 1851 Guthrie Carroll iagenweb.org/carroll
Cass 1851 Pottawattamie Atlantic iagenweb.org/cass
Cedar 1837 Wisconsin Territory Tipton iagenweb.org/cedar
Cerro Gordo 1851 Floyd Mason City iagenweb.org/cerrogordo
Cherokee 1851 Crawford Cherokee iagenweb.org/cherokee
Chickasaw 1851 Fayette New Hampton iagenweb.org/chickasaw
Clarke 1846 Lucas Osceola iagenweb.org/clarke
Clay 1851 Indian Lands Spencer iagenweb.org/clay
Clayton 1837 Dubuque, Wisconsin Territory Elkader iagenweb.org/clayton
Clinton 1837 Dubuque, Wisconsin Territory Clinton iagenweb.org/clinton
Cook County 1836 from Demoin & Dubuque; extinct    
Crawford 1851 Shelby Denison iagenweb.org/crawford
Dallas 1846 Polk Adel iagenweb.org/dallas
Davis 1843 Van Buren Bloomfield iagenweb.org/davis
Decatur 1846 Appanoose Leon iagenweb.org/decatur
Delaware 1837 Dubuque, Wisconsin Territory Manchester iagenweb.org/delaware
Des Moines (Originally Demoine) 1834 Michigan Territory; 1836 Wisconsin Territory Burlington iagenweb.org/desmoines
Dickinson 1851 Kossuth Spirit Lake iagenweb.org/dickinson
Dubuque 1834 Michigan Territory; 1836 Wisconsin Territory Dubuque iagenweb.org/dubuque
Emmet 1851 Kossuth, Dickinson Estherville iagenweb.org/emmet
Fayette 1837 Clayton, Wisconsin Territory West Union iagenweb.org/fayette
Floyd 1851 Chickasaw Charles City iagenweb.org/floyd
Fox 1851 1855, renamed Calhoun    
Franklin 1851 Chickasaw Hampton iagenweb.org/franklin
Fremont 1847 Pottawattamie Sidney iagenweb.org/fremont
Greene 1851 Dallas Jefferson iagenweb.org/greene
Grundy 1851 Black Hawk Grundy Center iagenweb.org/grundy
Guthrie 1851 Jackson Guthrie Center iagenweb.org/guthrie
Hamilton 1856 Webster Webster City iagenweb.org/hamilton
Hancock 1851 Wright Garner iagenweb.org/hancock
Hardin 1851 Black Hawk Eldora iagenweb.org/hardin
Harrison 1851 Pottawattamie Logan iagenweb.org/harrison
Henry 1836 Wisconsin Territory Mount Pleasant iagenweb.org/henry
Howard 1851 Chickasaw, Floyd Cresco iagenweb.org/howard
Humboldt 1851 Webster (originally spelled Humbolt) Dakota City iagenweb.org/humboldt
Ida 1851 Cherokee Ida Grove iagenweb.org/ida
Iowa 1843 Washington Marengo iagenweb.org/iowa
Jackson 1837 Wisconsin Territory Maquoketa iagenweb.org/jackson
Jasper 1846 Mahaska Newton iagenweb.org/jasper
Jefferson 1839 Indian Land Purchase Fairfield iagenweb.org/jefferson
Johnson 1837 Des Moines, Wisconsin Territory Iowa City iagenweb.org/johnson
Jones 1837 Wisconsin Territory Anamosa iagenweb.org/jones
Keokuk 1837 Wisconsin Territory; extinct    
Keokuk 1843 Washington Sigourney iagenweb.org/keokuk
Kishkekosh   changed to Monroe, 1846    
Kossuth 1851 Webster Algona iagenweb.org/kossuth
Lee 1836 Des Moines Fort Madison iagenweb.org/lee
Linn 1837 Wisconsin Territory Cedar Rapids iagenweb.org/linn
Louisa 1836 Des Moines Wapello iagenweb.org/louisa
Lucas 1846 Monroe Chariton iagenweb.org/lucas
Lyon 1851 Woodbury Rock Rapids iagenweb.org/lyon
Madison 1844 extinct    
Madison 1846 Polk Winterset iagenweb.org/madison
Mahaska 1843 Fox, Sac Indian Purchase Oskaloosa iagenweb.org/mahaska
Marion 1845 Washington Knoxville iagenweb.org/marion
Marshall 1846 Jasper Marshalltown iagenweb.org/marshall
Mills 1851 Pottawattamie Glenwood iagenweb.org/mills
Mitchell 1851 Chickasaw Osage iagenweb.org/mitchell
Monona 1851 Harrison Onawa iagenweb.org/monona
Monroe 1843 Monroe (formerly Kishkekosh) Albia iagenweb.org/monroe
Montgomery 1851 Polk Red Oak iagenweb.org/montgomery
Muscatine 1836 Des Moines Muscatine iagenweb.org/muscatine
O'Brien 1851 Cherokee Primghar iagenweb.org/obrien
Osceola 1851 Woodbury Sibley iagenweb.org/osceola
Page 1847 Pottawattamie Clarinda iagenweb.org/page
Palo Alto 1858 Kossuth Emmetsburg iagenweb.org/paloalto
Plymouth 1851 Woodbury Le Mars iagenweb.org/plymouth
Pocahontas 1851 Humboldt, Greene Pocahontas iagenweb.org/pocahontas
Polk 1846 Indian Lands Des Moines iagenweb.org/polk
Pottawattamie 1848 Indian Lands Council Bluffs iagenweb.org/pottawattamie
Poweshiek 1843 Mesquakie Indian Lands Montezuma iagenweb.org/poweshiek
Ringgold 1847 Taylor Mount Ayr iagenweb.org/ringgold
Risley 1851 changed to Webster 1853    
Sac 1851 Greene Sac City iagenweb.org/sac
Scott 1837 Wisconsin Territory Davenport iagenweb.org/scott
Shelby 1851 Cass Harlan iagenweb.org/shelby
Sioux 1851 Plymouth Orange City iagenweb.org/sioux
Slaughter 1837 Wisconsin Territory; renamed Washington, 1838    
Story 1846 Jasper, Polk, Boone Nevada iagenweb.org/story
Tama 1843 Boone, Benton Toledo iagenweb.org/tama
Taylor 1847 Page Bedford iagenweb.org/taylor
Union 1851 Clarke Creston iagenweb.org/union
Van Buren 1836 Des Moines Keosauqua iagenweb.org/vanburen
Wahkaw 1851 changed to Woodbury, 1853    
Wapello 1843 Indian Lands Ottumwa iagenweb.org/wapello
Warren 1846 Polk Indianola iagenweb.org/warren
Washington 1837 Wisconsin Territory; formerly Slaughter Washington iagenweb.org/washington
Wayne 1846 Appanoose Corydon iagenweb.org/wayne
Webster 1851 Yell, Risley Fort Dodge iagenweb.org/webster
Winnebago 1851 Kossuth Forest City iagenweb.org/winnebago
Winneshiek 1847 Indian Lands Decorah iagenweb.org/winneshiek
Woodbury 1851 Indian Lands (formerly Wahkaw) Sioux City iagenweb.org/woodbury
Worth 1851 Mitchell Northwood iagenweb.org/worth
Wright 1851 Webster Clarion iagenweb.org/wright
Yell 1851 extinct    

Sources consulted include 1904 Iowa Official Register, The Handy Book for Genealogists and Histories of Iowa Counties.
Prepared by Greta Thompson, August, 2004.