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List of counties in Iowa facts for kids

Kids Encyclopedia Facts
See also: List of United States counties and county-equivalents
Counties of Iowa
Location State of Iowa
Number 99
Populations 4,029 (Adams) – 430,640 (Polk)
Areas 381 square miles (990 km2) (Dickinson) – 973 square miles (2,520 km2) (Kossuth)
Government County government
Subdivisions cities, towns, townships, unincorporated communities, census designated place

There are 99 counties in the U.S. state of Iowa. The first two counties, Des Moines County and Dubuque County, were created in 1834 when Iowa was still part of the Michigan Territory. In preparation for Michigan's statehood, part of Michigan Territory was formed into Wisconsin Territory in 1836. Two years later, the western portion was split off to become Iowa Territory. The south-eastern part of Iowa Territory became Iowa, the 29th state in the union, on 28 December 1846, by which point 44 counties had been created. Counties continued to be created by the state government until 1857, when the last county, Humboldt County, was created. One of the most significant days in Iowa county history was January 15, 1851, on which 49 counties were created.

Iowa counties with numbers
Map of counties numbered as in the National Atlas of the United States

The Iowa Constitution of 1857, which is still in effect today, states that counties must have an area of at least 432 square miles (1,120 km2), and no county may be reduced below that size by boundary changes. However, exceptions to this rule were granted, as ten counties have areas below this size. (The table below shows land area, but the Constitution deals with total area.) The smallest county (Dickinson) has a land area of 381 sq mi (990 km2), while the largest (Kossuth) has an area 973 sq mi (2,520 km²). Polk County is the most densely populated county at 756/sq mi (292/km2), an increase in density from 2000 when it was 657 inhabitants per square mile (254/km2). Polk County contains the state's capital and largest city, Des Moines. In addition Iowa has one of the fewest number of counties whose boundaries are dictated by natural means, the vast majority of which being formed by lines of survey instead, resulting in a large number of "box counties".


County information

The number in the column headed "#" is the one used on the map from the National Atlas of the United States, shown on the left. The Federal Information Processing Standard (FIPS) code, which is used by the United States government to uniquely identify counties, is provided with each entry. The FIPS code for each county links to census data for that county.

County
FIPS Code

County seat

#

Established

Formed from

Etymology
Population
Area
Map
Adair County 001 Greenfield 69 January 15, 1851 Cass County John Adair (1757–1840), sixth governor of Kentucky &&&&&&&&&&&07682.&&&&&07,682 &&&&&&&&&&&&0569.&&&&&0569 sq mi
(&&&&&&&&&&&01474.&&&&&01,474 km²)
State map highlighting Adair County
Adams County 003 Corning 81 January 15, 1851 Taylor County John Adams, second President of the United States (1797–1801) &&&&&&&&&&&04029.&&&&&04,029 &&&&&&&&&&&&0424.&&&&&0424 sq mi
(&&&&&&&&&&&01098.&&&&&01,098 km²)
State map highlighting Adams County
Allamakee County 005 Waukon 11 February 20, 1847 Clayton County Disputed, possibly named for Allan Makee, an early Indian trader and guide for early settlers &&&&&&&&&&014330.&&&&&014,330 &&&&&&&&&&&&0640.&&&&&0640 sq mi
(&&&&&&&&&&&01658.&&&&&01,658 km²)
State map highlighting Allamakee County
Appanoose County 007 Centerville 96 February 17, 1843 Davis County Appanoose, Native American chief who headed peace party in the Black Hawk War &&&&&&&&&&012884.&&&&&012,884 &&&&&&&&&&&&0496.&&&&&0496 sq mi
(&&&&&&&&&&&01285.&&&&&01,285 km²)
State map highlighting Appanoose County


Audubon County 009 Audubon 57 January 15, 1851 Black Hawk County and Cass County John James Audubon (1785–1851), ornithologist and artist &&&&&&&&&&&06119.&&&&&06,119 &&&&&&&&&&&&0443.&&&&&0443 sq mi
(&&&&&&&&&&&01147.&&&&&01,147 km²)
State map highlighting Audubon County
Benton County 011 Vinton 51 December 21, 1837 Native American lands and Wisconsin Territory Thomas Hart Benton, United States Senator (1821–1851) &&&&&&&&&&026076.&&&&&026,076 &&&&&&&&&&&&0716.&&&&&0716 sq mi
(&&&&&&&&&&&01854.&&&&&01,854 km²)
State map highlighting Benton County
Black Hawk County 013 Waterloo 39 February 17, 1843 Delaware County Black Hawk (1767–1838), chief of Fox and Sac Indians and leader in the Black Hawk War &&&&&&&&&0131090.&&&&&0131,090 &&&&&&&&&&&&0567.&&&&&0567 sq mi
(&&&&&&&&&&&01469.&&&&&01,469 km²)
State map highlighting Black Hawk County
Boone County 015 Boone 47 January 13, 1846 Polk County Nathan Boone (1781–1863), one of the first to survey Iowa &&&&&&&&&&026306.&&&&&026,306 &&&&&&&&&&&&0572.&&&&&0572 sq mi
(&&&&&&&&&&&01481.&&&&&01,481 km²)
State map highlighting Boone County
Bremer County 017 Waverly 30 January 15, 1851 Native American lands and Winnebago County Fredrika Bremer (1801–1865), Swedish poet and author &&&&&&&&&&024276.&&&&&024,276 &&&&&&&&&&&&0428.&&&&&0428 sq mi
(&&&&&&&&&&&01109.&&&&&01,109 km²)
State map highlighting Bremer County
Buchanan County 019 Independence 40 December 21, 1837 Delaware County and Wisconsin Territory James Buchanan, fifteenth President of the United States (1857–1861) &&&&&&&&&&020958.&&&&&020,958 &&&&&&&&&&&&0571.&&&&&0571 sq mi
(&&&&&&&&&&&01479.&&&&&01,479 km²)
State map highlighting Buchanan County
Buena Vista County 021 Storm Lake 24 January 15, 1851 Clay County and Sac County Battle of Buena Vista, a battle during the Mexican-American War &&&&&&&&&&020260.&&&&&020,260 &&&&&&&&&&&&0575.&&&&&0575 sq mi
(&&&&&&&&&&&01489.&&&&&01,489 km²)
State map highlighting Buena Vista County
Butler County 023 Allison 29 January 15, 1851 Black Hawk County and Buchanan County William Orlando Butler (1791–1880), War of 1812 hero and unsuccessful candidate for Vice President &&&&&&&&&&014867.&&&&&014,867 &&&&&&&&&&&&0580.&&&&&0580 sq mi
(&&&&&&&&&&&01502.&&&&&01,502 km²)
State map highlighting Butler County
Calhoun County 025 Rockwell City 34 January 15, 1851 Fox County (renamed) John Caldwell Calhoun, Vice President of the United States (1825–1832) &&&&&&&&&&&09670.&&&&&09,670 &&&&&&&&&&&&0570.&&&&&0570 sq mi
(&&&&&&&&&&&01476.&&&&&01,476 km²)
State map highlighting Calhoun County
Carroll County 027 Carroll 45 January 15, 1851 Guthrie County Charles Carroll (1737–1832), longest lived signatory of the Declaration of Independence &&&&&&&&&&020816.&&&&&020,816 &&&&&&&&&&&&0569.&&&&&0569 sq mi
(&&&&&&&&&&&01474.&&&&&01,474 km²)
State map highlighting Carroll County
Cass County 029 Atlantic 68 January 15, 1851 Pottawattamie County Lewis Cass, United States Senator from Michigan and unsuccessful candidate for President (1848) &&&&&&&&&&013956.&&&&&013,956 &&&&&&&&&&&&0564.&&&&&0564 sq mi
(&&&&&&&&&&&01461.&&&&&01,461 km²)
State map highlighting Cass County
Cedar County 031 Tipton 65 December 21, 1837 Wisconsin Territory Red Cedar River, river which runs through county &&&&&&&&&&018499.&&&&&018,499 &&&&&&&&&&&&0580.&&&&&0580 sq mi
(&&&&&&&&&&&01502.&&&&&01,502 km²)
State map highlighting Cedar County
Cerro Gordo County 033 Mason City 17 January 15, 1851 Floyd County Battle of Cerro Gordo, battle during the Mexican-American War &&&&&&&&&&044151.&&&&&044,151 &&&&&&&&&&&&0568.&&&&&0568 sq mi
(&&&&&&&&&&&01471.&&&&&01,471 km²)
State map highlighting Cerro Gordo County
Cherokee County 035 Cherokee 23 January 15, 1851 Crawford County Cherokee Native American tribe &&&&&&&&&&012072.&&&&&012,072 &&&&&&&&&&&&0577.&&&&&0577 sq mi
(&&&&&&&&&&&01494.&&&&&01,494 km²)
State map highlighting Cherokee County
Chickasaw County 037 New Hampton 19 January 15, 1851 Fayette County Chickasaw Native American tribe &&&&&&&&&&012439.&&&&&012,439 &&&&&&&&&&&&0505.&&&&&0505 sq mi
(&&&&&&&&&&&01308.&&&&&01,308 km²)
State map highlighting Chickasaw County
Clarke County 039 Osceola 83 January 13, 1846 Lucas County James Clarke, third Governor of Iowa Territory (1845–1846) &&&&&&&&&&&09286.&&&&&09,286 &&&&&&&&&&&&0431.&&&&&0431 sq mi
(&&&&&&&&&&&01116.&&&&&01,116 km²)
State map highlighting Clarke County
Clay County 041 Spencer 14 January 15, 1851 Native American lands Henry Clay, Jr. (1807–1847), officer in the Mexican-American War &&&&&&&&&&016667.&&&&&016,667 &&&&&&&&&&&&0569.&&&&&0569 sq mi
(&&&&&&&&&&&01474.&&&&&01,474 km²)
State map highlighting Clay County
Clayton County 043 Elkader 21 December 21, 1837 Dubuque County and Wisconsin Territory John M. Clayton (1796–1856), United States Senator from Delaware &&&&&&&&&&018129.&&&&&018,129 &&&&&&&&&&&&0779.&&&&&0779 sq mi
(&&&&&&&&&&&02018.&&&&&02,018 km²)
State map highlighting Clayton County
Clinton County 045 Clinton 66 December 21, 1837 Dubuque County and Wisconsin Territory DeWitt Clinton (1769–1828), Governor of New York &&&&&&&&&&049116.&&&&&049,116 &&&&&&&&&&&&0695.&&&&&0695 sq mi
(&&&&&&&&&&&01800.&&&&&01,800 km²)
State map highlighting Clinton County
Crawford County 047 Denison 44 January 15, 1851 Shelby County William Harris Crawford (1772–1834), United States Senator from Georgia &&&&&&&&&&017096.&&&&&017,096 &&&&&&&&&&&&0714.&&&&&0714 sq mi
(&&&&&&&&&&&01849.&&&&&01,849 km²)
State map highlighting Crawford County
Dallas County 049 Adel 59 January 13, 1846 Polk County George Mifflin Dallas (1792–1864), eleventh Vice President of the United States &&&&&&&&&&066135.&&&&&066,135 &&&&&&&&&&&&0586.&&&&&0586 sq mi
(&&&&&&&&&&&01518.&&&&&01,518 km²)
State map highlighting Dallas County
Davis County 051 Bloomfield 97 February 17, 1843 Van Buren County Garrett Davis (1801–1872), congressman &&&&&&&&&&&08753.&&&&&08,753 &&&&&&&&&&&&0503.&&&&&0503 sq mi
(&&&&&&&&&&&01303.&&&&&01,303 km²)
State map highlighting Davis County
Decatur County 053 Leon 94 January 13, 1846 Appanoose County Stephen Decatur (1779–1820), naval officer in the War of 1812 &&&&&&&&&&&08457.&&&&&08,457 &&&&&&&&&&&&0532.&&&&&0532 sq mi
(&&&&&&&&&&&01378.&&&&&01,378 km²)
State map highlighting Decatur County
Delaware County 055 Manchester 41 December 21, 1837 Dubuque County and Wisconsin Territory State of Delaware, home of Iowa statehood advocate U.S. Senator John M. Clayton &&&&&&&&&&017764.&&&&&017,764 &&&&&&&&&&&&0578.&&&&&0578 sq mi
(&&&&&&&&&&&01497.&&&&&01,497 km²)
State map highlighting Delaware County
Des Moines County 057 Burlington 89 September 6, 1834 Michigan Territory and Wisconsin Territory Des Moines River, river that once ran through the county &&&&&&&&&&040325.&&&&&040,325 &&&&&&&&&&&&0416.&&&&&0416 sq mi
(&&&&&&&&&&&01077.&&&&&01,077 km²)
State map highlighting Des Moines County
Dickinson County 059 Spirit Lake 3 January 15, 1851 Kossuth County Daniel Stevens Dickinson (1800–1866), United States Senator from New York &&&&&&&&&&016667.&&&&&016,667 &&&&&&&&&&&&0381.&&&&&0381 sq mi
(&&&&&&&&&&&&0987.&&&&&0987 km²)
State map highlighting Dickinson County
Dubuque County 061 Dubuque 42 September 6, 1834 Michigan Territory and Wisconsin Territory Julien Dubuque (1762–1810), first permanent white settler in Iowa &&&&&&&&&&093653.&&&&&093,653 &&&&&&&&&&&&0608.&&&&&0608 sq mi
(&&&&&&&&&&&01575.&&&&&01,575 km²)
State map highlighting Dubuque County
Emmet County 063 Estherville 4 January 15, 1851 Dickinson County and Kossuth County Robert Emmet (1778–1803), Irish revolutionary and American republican sympathizer &&&&&&&&&&010302.&&&&&010,302 &&&&&&&&&&&&0396.&&&&&0396 sq mi
(&&&&&&&&&&&01026.&&&&&01,026 km²)
State map highlighting Emmet County
Fayette County 065 West Union 20 December 21, 1837 Clayton County and Wisconsin Territory Marquis de Lafayette (1757–1834), Frenchman who aided colonial forces during the American Revolutionary War &&&&&&&&&&020880.&&&&&020,880 &&&&&&&&&&&&0731.&&&&&0731 sq mi
(&&&&&&&&&&&01893.&&&&&01,893 km²)
State map highlighting Fayette County
Floyd County 067 Charles City 18 January 15, 1851 Chickasaw County Charles Floyd (1782–1804), member of the Lewis and Clark Expedition who died in Iowa &&&&&&&&&&016303.&&&&&016,303 &&&&&&&&&&&&0501.&&&&&0501 sq mi
(&&&&&&&&&&&01298.&&&&&01,298 km²)
State map highlighting Floyd County
Franklin County 069 Hampton 28 January 15, 1851 Chickasaw County Benjamin Franklin (1706–1790), statesman and U.S. founding father &&&&&&&&&&010680.&&&&&010,680 &&&&&&&&&&&&0582.&&&&&0582 sq mi
(&&&&&&&&&&&01507.&&&&&01,507 km²)
State map highlighting Franklin County
Fremont County 071 Sidney 90 February 24, 1847 Pottawattamie County John Charles Fremont (1813–1890), officer in Mexican-American War &&&&&&&&&&&07441.&&&&&07,441 &&&&&&&&&&&&0511.&&&&&0511 sq mi
(&&&&&&&&&&&01323.&&&&&01,323 km²)
State map highlighting Fremont County
Greene County 073 Jefferson 46 January 15, 1851 Dallas County Nathanael Greene (1742–1786), American Revolutionary War general &&&&&&&&&&&09336.&&&&&09,336 &&&&&&&&&&&&0568.&&&&&0568 sq mi
(&&&&&&&&&&&01471.&&&&&01,471 km²)
State map highlighting Greene County
Grundy County 075 Grundy Center 38 January 15, 1851 Black Hawk County Felix Grundy (1777–1840), United States Senator &&&&&&&&&&012453.&&&&&012,453 &&&&&&&&&&&&0503.&&&&&0503 sq mi
(&&&&&&&&&&&01303.&&&&&01,303 km²)
State map highlighting Grundy County
Guthrie County 077 Guthrie Center 58 July 8, 1851 Jackson County Edwin B. Guthrie, officer in Mexican-American War &&&&&&&&&&010954.&&&&&010,954 &&&&&&&&&&&&0591.&&&&&0591 sq mi
(&&&&&&&&&&&01531.&&&&&01,531 km²)
State map highlighting Guthrie County
Hamilton County 079 Webster City 36 December 22, 1856 Webster County William W. Hamilton, President of the Iowa Senate (1856–1857) &&&&&&&&&&015673.&&&&&015,673 &&&&&&&&&&&&0577.&&&&&0577 sq mi
(&&&&&&&&&&&01494.&&&&&01,494 km²)
State map highlighting Hamilton County
Hancock County 081 Garner 16 January 15, 1851 Wright County John Hancock (1737–1793), President of the First Continental Congress &&&&&&&&&&011341.&&&&&011,341 &&&&&&&&&&&&0571.&&&&&0571 sq mi
(&&&&&&&&&&&01479.&&&&&01,479 km²)
State map highlighting Hancock County
Hardin County 083 Eldora 37 January 15, 1851 Black Hawk County John J. Hardin (1810–1847), prominent soldier in the Black Hawk War &&&&&&&&&&017534.&&&&&017,534 &&&&&&&&&&&&0569.&&&&&0569 sq mi
(&&&&&&&&&&&01474.&&&&&01,474 km²)
State map highlighting Hardin County
Harrison County 085 Logan 55 January 15, 1851 Pottawattamie County William Henry Harrison (1773–1841), ninth President of the United States &&&&&&&&&&014928.&&&&&014,928 &&&&&&&&&&&&0697.&&&&&0697 sq mi
(&&&&&&&&&&&01805.&&&&&01,805 km²)
State map highlighting Harrison County
Henry County 087 Mount Pleasant 88 December 7, 1836 Wisconsin Territory Disputed; either Henry Dodge (1782–1867), governor of Wisconsin Territory; or James Dougherty Henry, general in the Black Hawk War &&&&&&&&&&020145.&&&&&020,145 &&&&&&&&&&&&0434.&&&&&0434 sq mi
(&&&&&&&&&&&01124.&&&&&01,124 km²)
State map highlighting Henry County
Howard County 089 Cresco 9 January 15, 1851 Chickasaw County Tilghman Ashurst Howard (1797–1844), congressman &&&&&&&&&&&09566.&&&&&09,566 &&&&&&&&&&&&0473.&&&&&0473 sq mi
(&&&&&&&&&&&01225.&&&&&01,225 km²)
State map highlighting Howard County
Humboldt County 091 Dakota City 26 February 26, 1857 Webster County Alexander von Humboldt (1769–1859), German scientist &&&&&&&&&&&09815.&&&&&09,815 &&&&&&&&&&&&0434.&&&&&0434 sq mi
(&&&&&&&&&&&01124.&&&&&01,124 km²)
State map highlighting Humboldt County
Ida County 093 Ida Grove 32 January 15, 1851 Cherokee County Mount Ida in Greece &&&&&&&&&&&07089.&&&&&07,089 &&&&&&&&&&&&0432.&&&&&0432 sq mi
(&&&&&&&&&&&01119.&&&&&01,119 km²)
State map highlighting Ida County
Iowa County 095 Marengo 63 February 17, 1843 Washington County Iowa River, river that flows through the county, and which is itself named for the Ioway Native American tribe &&&&&&&&&&016355.&&&&&016,355 &&&&&&&&&&&&0586.&&&&&0586 sq mi
(&&&&&&&&&&&01518.&&&&&01,518 km²)
State map highlighting Iowa County
Jackson County 097 Maquoketa 54 December 21, 1837 Wisconsin Territory Andrew Jackson (1767–1845), seventh President of the United States &&&&&&&&&&019848.&&&&&019,848 &&&&&&&&&&&&0636.&&&&&0636 sq mi
(&&&&&&&&&&&01647.&&&&&01,647 km²)
State map highlighting Jackson County
Jasper County 099 Newton 61 January 13, 1846 Mahaska County William Jasper (1750–1779), sergeant in the American Revolutionary War &&&&&&&&&&036842.&&&&&036,842 &&&&&&&&&&&&0730.&&&&&0730 sq mi
(&&&&&&&&&&&01891.&&&&&01,891 km²)
State map highlighting Jasper County
Jefferson County 101 Fairfield 87 January 21, 1839 Native American lands Thomas Jefferson (1743–1826), third President of the United States &&&&&&&&&&016843.&&&&&016,843 &&&&&&&&&&&&0435.&&&&&0435 sq mi
(&&&&&&&&&&&01127.&&&&&01,127 km²)
State map highlighting Jefferson County
Johnson County 103 Iowa City 64 December 21, 1837 Des Moines County, Iowa and Wisconsin Territory Richard Mentor Johnson (1780–1850), Vice President of the United States 1837-1841 &&&&&&&&&0130882.&&&&&0130,882 &&&&&&&&&&&&0614.&&&&&0614 sq mi
(&&&&&&&&&&&01590.&&&&&01,590 km²)
State map highlighting Johnson County
Jones County 105 Anamosa 53 December 21, 1837 Wisconsin Territory George Wallace Jones (1804–1896), United States Senator from Iowa &&&&&&&&&&020638.&&&&&020,638 &&&&&&&&&&&&0575.&&&&&0575 sq mi
(&&&&&&&&&&&01489.&&&&&01,489 km²)
State map highlighting Jones County
Keokuk County 107 Sigourney 74 December 21, 1837 Washington County Keokuk (1767–1848), chief of the Sac Native American tribe &&&&&&&&&&010511.&&&&&010,511 &&&&&&&&&&&&0579.&&&&&0579 sq mi
(&&&&&&&&&&&01500.&&&&&01,500 km²)
State map highlighting Keokuk County
Kossuth County 109 Algona 5 January 15, 1851 Webster County Lajos Kossuth (1802–1894), Hungarian revolutionary who was inspired by American democratic ideals &&&&&&&&&&015543.&&&&&015,543 &&&&&&&&&&&&0973.&&&&&0973 sq mi
(&&&&&&&&&&&02520.&&&&&02,520 km²)
State map highlighting Kossuth County
Lee County 111 Fort Madison and Keokuk 99 December 7, 1836 Des Moines County William Elliott Lee, businessman from the New York Land Company, which sold the county's first tracts of land &&&&&&&&&&035862.&&&&&035,862 &&&&&&&&&&&&0517.&&&&&0517 sq mi
(&&&&&&&&&&&01339.&&&&&01,339 km²)
State map highlighting Lee County
Linn County 113 Cedar Rapids 52 December 21, 1837 Wisconsin Territory Lewis Fields Linn (1795–1843), doctor and United States Senator from Missouri &&&&&&&&&0211226.&&&&&0211,226 &&&&&&&&&&&&0718.&&&&&0718 sq mi
(&&&&&&&&&&&01860.&&&&&01,860 km²)
State map highlighting Linn County
Louisa County 115 Wapello 76 December 7, 1836 Des Moines County Disputed; either Louisa Massey, a woman then famous for avenging the death of her brother; or Louisa County, Virginia &&&&&&&&&&011387.&&&&&011,387 &&&&&&&&&&&&0402.&&&&&0402 sq mi
(&&&&&&&&&&&01041.&&&&&01,041 km²)
State map highlighting Louisa County
Lucas County 117 Chariton 84 January 13, 1846 Monroe County Robert Lucas (1781–1853), first Governor of Iowa Territory &&&&&&&&&&&08898.&&&&&08,898 &&&&&&&&&&&&0431.&&&&&0431 sq mi
(&&&&&&&&&&&01116.&&&&&01,116 km²)
State map highlighting Lucas County
Lyon County 119 Rock Rapids 1 January 15, 1851 Woodbury County, Iowa Nathaniel Lyon (1818–1861), first Union general to be killed in the American Civil War, (formerly named Buncombe County) &&&&&&&&&&011581.&&&&&011,581 &&&&&&&&&&&&0588.&&&&&0588 sq mi
(&&&&&&&&&&&01523.&&&&&01,523 km²)
State map highlighting Lyon County
Madison County 121 Winterset 70 January 13, 1846 Polk County James Madison (1751–1836), fourth President of the United States &&&&&&&&&&015679.&&&&&015,679 &&&&&&&&&&&&0561.&&&&&0561 sq mi
(&&&&&&&&&&&01453.&&&&&01,453 km²)
State map highlighting Madison County
Mahaska County 123 Oskaloosa 73 February 17, 1843 Fox and Sac Indian lands Mahaska (1784–1834), chief of the Ioway Native American tribe &&&&&&&&&&022381.&&&&&022,381 &&&&&&&&&&&&0571.&&&&&0571 sq mi
(&&&&&&&&&&&01479.&&&&&01,479 km²)
State map highlighting Mahaska County
Marion County 125 Knoxville 72 June 10, 1845 Washington County Francis Marion (1732–1795), general in the American Revolutionary War &&&&&&&&&&033309.&&&&&033,309 &&&&&&&&&&&&0554.&&&&&0554 sq mi
(&&&&&&&&&&&01435.&&&&&01,435 km²)
State map highlighting Marion County
Marshall County 127 Marshalltown 49 January 13, 1846 Jasper County John Marshall (1755–1835), fourth Chief Justice of the United States Supreme Court &&&&&&&&&&040648.&&&&&040,648 &&&&&&&&&&&&0572.&&&&&0572 sq mi
(&&&&&&&&&&&01481.&&&&&01,481 km²)
State map highlighting Marshall County
Mills County 129 Glenwood 79 January 15, 1851 Pottawattamie County Frederick Mills, major killed during the Battle of Churubusco in the Mexican-American War &&&&&&&&&&015059.&&&&&015,059 &&&&&&&&&&&&0437.&&&&&0437 sq mi
(&&&&&&&&&&&01132.&&&&&01,132 km²)
State map highlighting Mills County
Mitchell County 131 Osage 8 January 15, 1851 Chickasaw County John Mitchel (1815–1875), Irish revolutionary who for a time operated out of the United States &&&&&&&&&&010776.&&&&&010,776 &&&&&&&&&&&&0469.&&&&&0469 sq mi
(&&&&&&&&&&&01215.&&&&&01,215 km²)
State map highlighting Mitchell County
Monona County 133 Onawa 43 January 15, 1851 Harrison County Word of Native American origin that perhaps translates to "peaceful valley" &&&&&&&&&&&09243.&&&&&09,243 &&&&&&&&&&&&0693.&&&&&0693 sq mi
(&&&&&&&&&&&01795.&&&&&01,795 km²)
State map highlighting Monona County
Monroe County 135 Albia 85 February 17, 1843 Wapello County James Monroe (1758–1831), fifth President of the United States &&&&&&&&&&&07970.&&&&&07,970 &&&&&&&&&&&&0433.&&&&&0433 sq mi
(&&&&&&&&&&&01121.&&&&&01,121 km²)
State map highlighting Monroe County
Montgomery County 137 Red Oak 80 January 15, 1851 Polk County Richard Montgomery (1738–1775), general in the American Revolutionary War &&&&&&&&&&010740.&&&&&010,740 &&&&&&&&&&&&0424.&&&&&0424 sq mi
(&&&&&&&&&&&01098.&&&&&01,098 km²)
State map highlighting Montgomery County
Muscatine County 139 Muscatine 77 December 7, 1836 Des Moines County Muscatine Native American tribe &&&&&&&&&&042745.&&&&&042,745 &&&&&&&&&&&&0439.&&&&&0439 sq mi
(&&&&&&&&&&&01137.&&&&&01,137 km²)
State map highlighting Muscatine County
O'Brien County 141 Primghar 13 January 15, 1851 Cherokee County William Smith O'Brien (1803–1864), Irish revolutionary who was inspired by American democratic ideals &&&&&&&&&&014398.&&&&&014,398 &&&&&&&&&&&&0573.&&&&&0573 sq mi
(&&&&&&&&&&&01484.&&&&&01,484 km²)
State map highlighting O'Brien County
Osceola County 143 Sibley 2 January 15, 1851 Woodbury County Osceola (1804–1838), Native American leader &&&&&&&&&&&06462.&&&&&06,462 &&&&&&&&&&&&0399.&&&&&0399 sq mi
(&&&&&&&&&&&01033.&&&&&01,033 km²)
State map highlighting Osceola County
Page County 145 Clarinda 91 February 24, 1847 Pottawattamie County John Page, officer killed in Battle of Palo Alto in the Mexican-American War &&&&&&&&&&015932.&&&&&015,932 &&&&&&&&&&&&0535.&&&&&0535 sq mi
(&&&&&&&&&&&01386.&&&&&01,386 km²)
State map highlighting Page County
Palo Alto County 147 Emmetsburg 15 January 15, 1851 Kossuth County Battle of Palo Alto in the Mexican-American War &&&&&&&&&&&09421.&&&&&09,421 &&&&&&&&&&&&0564.&&&&&0564 sq mi
(&&&&&&&&&&&01461.&&&&&01,461 km²)
State map highlighting Palo Alto County
Plymouth County 149 Le Mars 22 January 15, 1851 Woodbury County Landing place of the Pilgrims who came to America on the Mayflower &&&&&&&&&&024986.&&&&&024,986 &&&&&&&&&&&&0864.&&&&&0864 sq mi
(&&&&&&&&&&&02238.&&&&&02,238 km²)
State map highlighting Plymouth County
Pocahontas County 151 Pocahontas 25 January 15, 1851 Greene County and Humboldt County Pocahontas (1595–1618), famous Native American woman &&&&&&&&&&&07310.&&&&&07,310 &&&&&&&&&&&&0578.&&&&&0578 sq mi
(&&&&&&&&&&&01497.&&&&&01,497 km²)
State map highlighting Pocahontas County
Polk County 153 Des Moines 60 January 13, 1846 Native American lands James K. Polk (1795–1849), eleventh President of the United States &&&&&&&&&0430640.&&&&&0430,640 &&&&&&&&&&&&0570.&&&&&0570 sq mi
(&&&&&&&&&&&01476.&&&&&01,476 km²)
State map highlighting Polk County
Pottawattamie County 155 Council Bluffs 67 February 24, 1847 Native American lands Pottawattamie Native American tribe &&&&&&&&&&093158.&&&&&093,158 &&&&&&&&&&&&0954.&&&&&0954 sq mi
(&&&&&&&&&&&02471.&&&&&02,471 km²)
State map highlighting Pottawattamie County
Poweshiek County 157 Montezuma 62 February 17, 1843 Mesquakie Indian lands Poweshiek, chief of the Fox tribe &&&&&&&&&&018914.&&&&&018,914 &&&&&&&&&&&&0585.&&&&&0585 sq mi
(&&&&&&&&&&&01515.&&&&&01,515 km²)
State map highlighting Poweshiek County
Ringgold County 159 Mount Ayr 93 February 24, 1847 Taylor County Samuel Ringgold (1796–1846), major killed in the Mexican-American War &&&&&&&&&&&05131.&&&&&05,131 &&&&&&&&&&&&0538.&&&&&0538 sq mi
(&&&&&&&&&&&01393.&&&&&01,393 km²)
State map highlighting Ringgold County
Sac County 161 Sac City 33 January 15, 1851 Greene County Sac Native American tribe &&&&&&&&&&010350.&&&&&010,350 &&&&&&&&&&&&0576.&&&&&0576 sq mi
(&&&&&&&&&&&01492.&&&&&01,492 km²)
State map highlighting Sac County
Scott County 163 Davenport 78 December 21, 1837 Wisconsin Territory Winfield Scott (1786–1866), U.S. Army General during the War of 1812 &&&&&&&&&0165224.&&&&&0165,224 &&&&&&&&&&&&0458.&&&&&0458 sq mi
(&&&&&&&&&&&01186.&&&&&01,186 km²)
State map highlighting Scott County
Shelby County 165 Harlan 56 January 15, 1851 Cass County Isaac Shelby (1750–1826), general in the American Revolutionary War and the War of 1812 &&&&&&&&&&012167.&&&&&012,167 &&&&&&&&&&&&0591.&&&&&0591 sq mi
(&&&&&&&&&&&01531.&&&&&01,531 km²)
State map highlighting Shelby County
Sioux County 167 Orange City 12 January 15, 1851 Plymouth County Sioux Native American tribe &&&&&&&&&&033704.&&&&&033,704 &&&&&&&&&&&&0768.&&&&&0768 sq mi
(&&&&&&&&&&&01989.&&&&&01,989 km²)
State map highlighting Sioux County
Story County 169 Nevada 48 January 13, 1846 Boone County, Jasper County, and Polk County Joseph Story (1779–1845), United States Supreme Court justice &&&&&&&&&&089542.&&&&&089,542 &&&&&&&&&&&&0573.&&&&&0573 sq mi
(&&&&&&&&&&&01484.&&&&&01,484 km²)
State map highlighting Story County
Tama County 171 Toledo 50 February 17, 1843 Benton County and Boone County Disputed; either Taimah, Fox chief; or Taomah, wife of Poweshiek &&&&&&&&&&017767.&&&&&017,767 &&&&&&&&&&&&0721.&&&&&0721 sq mi
(&&&&&&&&&&&01867.&&&&&01,867 km²)
State map highlighting Tama County
Taylor County 173 Bedford 92 February 24, 1847 Page County Zachary Taylor (1784–1850), twelfth President of the United States &&&&&&&&&&&06317.&&&&&06,317 &&&&&&&&&&&&0534.&&&&&0534 sq mi
(&&&&&&&&&&&01383.&&&&&01,383 km²)
State map highlighting Taylor County
Union County 175 Creston 82 January 15, 1851 Clarke County The union of the states &&&&&&&&&&012534.&&&&&012,534 &&&&&&&&&&&&0424.&&&&&0424 sq mi
(&&&&&&&&&&&01098.&&&&&01,098 km²)
State map highlighting Union County
Van Buren County 177 Keosauqua 98 December 7, 1836 Des Moines County Martin Van Buren (1782–1862), eighth President of the United States &&&&&&&&&&&07570.&&&&&07,570 &&&&&&&&&&&&0485.&&&&&0485 sq mi
(&&&&&&&&&&&01256.&&&&&01,256 km²)
State map highlighting Van Buren County
Wapello County 179 Ottumwa 86 February 17, 1843 Native American lands Wapello, chief of the Fox Native American tribe &&&&&&&&&&035625.&&&&&035,625 &&&&&&&&&&&&0432.&&&&&0432 sq mi
(&&&&&&&&&&&01119.&&&&&01,119 km²)
State map highlighting Wapello County
Warren County 181 Indianola 71 January 13, 1846 Polk County Joseph Warren (1741–1775), General in the American Revolutionary War &&&&&&&&&&046225.&&&&&046,225 &&&&&&&&&&&&0572.&&&&&0572 sq mi
(&&&&&&&&&&&01481.&&&&&01,481 km²)
State map highlighting Warren County
Washington County 183 Washington 75 January 25, 1839 Wisconsin Territory George Washington (1732–1799), first President of the United States &&&&&&&&&&021704.&&&&&021,704 &&&&&&&&&&&&0569.&&&&&0569 sq mi
(&&&&&&&&&&&01474.&&&&&01,474 km²)
State map highlighting Washington County
Wayne County 185 Corydon 95 January 13, 1846 Appanoose County Anthony Wayne (1745–1796), General in the American Revolutionary War &&&&&&&&&&&06403.&&&&&06,403 &&&&&&&&&&&&0526.&&&&&0526 sq mi
(&&&&&&&&&&&01362.&&&&&01,362 km²)
State map highlighting Wayne County
Webster County 187 Fort Dodge 35 January 12, 1853 Risley County and Yell County (defunct counties) Daniel Webster (1782–1852), U.S. Senator from Massachusetts &&&&&&&&&&038013.&&&&&038,013 &&&&&&&&&&&&0715.&&&&&0715 sq mi
(&&&&&&&&&&&01852.&&&&&01,852 km²)
State map highlighting Webster County
Winnebago County 189 Forest City 6 January 15, 1851 Kossuth County Winnebago Native American tribe &&&&&&&&&&010866.&&&&&010,866 &&&&&&&&&&&&0400.&&&&&0400 sq mi
(&&&&&&&&&&&01036.&&&&&01,036 km²)
State map highlighting Winnebago County
Winneshiek County 191 Decorah 10 February 20, 1847 Native American lands Winneshiek, chief of the Winnebago Native American tribe &&&&&&&&&&021056.&&&&&021,056 &&&&&&&&&&&&0690.&&&&&0690 sq mi
(&&&&&&&&&&&01787.&&&&&01,787 km²)
State map highlighting Winneshiek County
Woodbury County 193 Sioux City 31 January 12, 1853 Polk County Levi Woodbury (1789–1851), Governor of New Hampshire, (formerly named Wahkaw County) &&&&&&&&&0102172.&&&&&0102,172 &&&&&&&&&&&&0873.&&&&&0873 sq mi
(&&&&&&&&&&&02261.&&&&&02,261 km²)
State map highlighting Woodbury County
Worth County 195 Northwood 7 January 15, 1851 Mitchell County William Jenkins Worth (1794–1849), officer in the Black Hawk War and the Mexican-American War &&&&&&&&&&&07598.&&&&&07,598 &&&&&&&&&&&&0400.&&&&&0400 sq mi
(&&&&&&&&&&&01036.&&&&&01,036 km²)
State map highlighting Worth County
Wright County 197 Clarion 27 January 15, 1851 Webster County and Kossuth County Silas Wright (1795–1847), Governor of New York, and Joseph Albert Wright (1810–1867), Governor of Indiana, brothers &&&&&&&&&&013229.&&&&&013,229 &&&&&&&&&&&&0581.&&&&&0581 sq mi
(&&&&&&&&&&&01505.&&&&&01,505 km²)
State map highlighting Wright County

Former counties

The following counties no longer exist:

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