County
| FIPS code[10]
| County seat[4]
| #
| Est.[4][11]
| Formed from[12]
| Etymology[11] | Map #
| Population[13] | Area[4] | Map |
|---|
| Adair County | 001 | Greenfield | 01 | Jan 15, 1851 | Cass County | John Adair,Kentucky Governor | 69 | 7,431 | 569 sq mi (1,474 km2) |  |
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| Adams County | 003 | Corning | 02 | Jan 15, 1851 | Taylor County | John Adams,US President | 81 | 3,606 | 424 sq mi (1,098 km2) |  |
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| Allamakee County | 005 | Waukon | 03 | Feb 20, 1847 | Clayton County | Disputed, possibly Allan Makee, early trader and guide for settlers, orMeskwakianamiki and/orOjibweanimikii both meaningthunder orthunderer[14]: 33 | 11 | 14,184 | 640 sq mi (1,658 km2) |  |
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| Appanoose County | 007 | Centerville | 04 | Feb 17, 1843 | Davis County | Chief Appanoose, headed peace party in theBlack Hawk War | 96 | 12,106 | 496 sq mi (1,285 km2) |  |
|---|
| Audubon County | 009 | Audubon | 05 | Jan 15, 1851 | Black Hawk County andCass County | John James Audubon, ornithologist and artist | 57 | 5,562 | 443 sq mi (1,147 km2) |  |
|---|
| Benton County | 011 | Vinton | 06 | Dec 21, 1837 | Native American lands andWisconsin Territory | Thomas Hart Benton,Missouri Senator | 51 | 25,799 | 716 sq mi (1,854 km2) |  |
|---|
| Black Hawk County | 013 | Waterloo | 07 | Feb 17, 1843 | Delaware County | Black Hawk, leader duringBlack Hawk War | 39 | 132,348 | 567 sq mi (1,469 km2) |  |
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| Boone County | 015 | Boone | 08 | Jan 13, 1846 | Polk County | Nathan Boone, one of the first to survey Iowa | 47 | 26,729 | 572 sq mi (1,481 km2) |  |
|---|
| Bremer County | 017 | Waverly | 09 | Jan 15, 1851 | Native American lands andWinnebago County | Fredrika Bremer, Swedish poet and author | 30 | 25,328 | 428 sq mi (1,109 km2) |  |
|---|
| Buchanan County | 019 | Independence | 10 | Dec 21, 1837 | Delaware County andWisconsin Territory | James Buchanan,US President | 40 | 20,733 | 571 sq mi (1,479 km2) |  |
|---|
| Buena Vista County | 021 | Storm Lake | 11 | Jan 15, 1851 | Clay County andSac County | Battle of Buena Vista,Mexican–American War | 24 | 20,816 | 575 sq mi (1,489 km2) |  |
|---|
| Butler County | 023 | Allison | 12 | Jan 15, 1851 | Black Hawk County andBuchanan County | William Orlando Butler,War of 1812 hero | 29 | 14,156 | 580 sq mi (1,502 km2) |  |
|---|
| Calhoun County | 025 | Rockwell City | 13 | Jan 15, 1851 | Fox County (renamed) | John C. Calhoun,US Vice President | 34 | 9,711 | 570 sq mi (1,476 km2) |  |
|---|
| Carroll County | 027 | Carroll | 14 | Jan 15, 1851 | Guthrie County | Charles Carroll, signatory of theDeclaration of Independence | 45 | 20,407 | 569 sq mi (1,474 km2) |  |
|---|
| Cass County | 029 | Atlantic | 15 | Jan 15, 1851 | Pottawattamie County | Lewis Cass,Michigan Senator | 68 | 13,024 | 564 sq mi (1,461 km2) |  |
|---|
| Cedar County | 031 | Tipton | 16 | Dec 21, 1837 | Wisconsin Territory | Cedar River that runs through county | 65 | 18,231 | 580 sq mi (1,502 km2) |  |
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| Cerro Gordo County | 033 | Mason City | 17 | Jan 15, 1851 | Floyd County | Battle of Cerro Gordo,Mexican–American War | 17 | 42,493 | 568 sq mi (1,471 km2) |  |
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| Cherokee County | 035 | Cherokee | 18 | Jan 15, 1851 | Crawford County | Cherokee People | 23 | 11,658 | 577 sq mi (1,494 km2) |  |
|---|
| Chickasaw County | 037 | New Hampton | 19 | Jan 15, 1851 | Fayette County | Chickasaw People | 19 | 11,719 | 505 sq mi (1,308 km2) |  |
|---|
| Clarke County | 039 | Osceola | 20 | Jan 13, 1846 | Lucas County | James Clarke,Governor ofIowa Territory | 83 | 9,524 | 431 sq mi (1,116 km2) |  |
|---|
| Clay County | 041 | Spencer | 21 | Jan 15, 1851 | Native American lands | Henry Clay, Jr., officer in theMexican–American War | 14 | 16,474 | 569 sq mi (1,474 km2) |  |
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| Clayton County | 043 | Elkader | 22 | Dec 21, 1837 | Dubuque County andWisconsin Territory | John M. Clayton,Delaware Senator | 21 | 16,931 | 779 sq mi (2,018 km2) |  |
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| Clinton County | 045 | Clinton | 23 | Dec 21, 1837 | Dubuque County andWisconsin Territory | DeWitt Clinton,New York Governor | 66 | 46,015 | 695 sq mi (1,800 km2) |  |
|---|
| Crawford County | 047 | Denison | 24 | Jan 15, 1851 | Shelby County | William Harris Crawford,Georgia Senator | 44 | 16,378 | 714 sq mi (1,849 km2) |  |
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| Dallas County | 049 | Adel | 25 | Jan 13, 1846 | Polk County | George Mifflin Dallas,US Vice President | 59 | 115,343 | 586 sq mi (1,518 km2) |  |
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| Davis County | 051 | Bloomfield | 26 | Feb 17, 1843 | Van Buren County | Garrett Davis,Kentucky Congressman | 97 | 9,193 | 503 sq mi (1,303 km2) |  |
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| Decatur County | 053 | Leon | 27 | Jan 13, 1846 | Appanoose County | Stephen Decatur,War of 1812 naval officer | 94 | 7,656 | 532 sq mi (1,378 km2) |  |
|---|
| Delaware County | 055 | Manchester | 28 | Dec 21, 1837 | Dubuque County andWisconsin Territory | State ofDelaware, home of Iowa statehood advocateUS SenatorJohn M. Clayton | 41 | 17,609 | 578 sq mi (1,497 km2) |  |
|---|
| Des Moines County | 057 | Burlington | 29 | Sep 6, 1834 | Michigan Territory andWisconsin Territory | Des Moines River that once ran through the county | 89 | 38,411 | 416 sq mi (1,077 km2) |  |
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| Dickinson County | 059 | Spirit Lake | 30 | Jan 15, 1851 | Kossuth County | Daniel Stevens Dickinson,New York Senator | 3 | 18,158 | 381 sq mi (987 km2) |  |
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| Dubuque County | 061 | Dubuque | 31 | Sep 6, 1834 | Michigan Territory andWisconsin Territory | Julien Dubuque, first permanent white settler in Iowa | 42 | 99,242 | 608 sq mi (1,575 km2) |  |
|---|
| Emmet County | 063 | Estherville | 32 | Jan 15, 1851 | Dickinson County andKossuth County | Robert Emmet, Irish revolutionary and American republican sympathizer | 4 | 9,162 | 396 sq mi (1,026 km2) |  |
|---|
| Fayette County | 065 | West Union | 33 | Dec 21, 1837 | Clayton County andWisconsin Territory | Marquis de Lafayette, Frenchman who aided colonial forces duringAmerican Revolutionary War | 20 | 19,152 | 731 sq mi (1,893 km2) |  |
|---|
| Floyd County | 067 | Charles City | 34 | Jan 15, 1851 | Chickasaw County | Charles Floyd, member ofLewis and Clark Expedition who died in Iowa | 18 | 15,008 | 501 sq mi (1,298 km2) |  |
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| Franklin County | 069 | Hampton | 35 | Jan 15, 1851 | Chickasaw County | Benjamin Franklin, statesman and US founding father | 28 | 10,024 | 582 sq mi (1,507 km2) |  |
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| Fremont County | 071 | Sidney | 36 | Feb 24, 1847 | Pottawattamie County | John Charles Fremont,Mexican–American War officer | 90 | 6,494 | 511 sq mi (1,323 km2) |  |
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| Greene County | 073 | Jefferson | 37 | Jan 15, 1851 | Dallas County | Nathanael Greene,American Revolutionary War general | 46 | 8,662 | 568 sq mi (1,471 km2) |  |
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| Grundy County | 075 | Grundy Center | 38 | Jan 15, 1851 | Black Hawk County | Felix Grundy,Tennessee Congressman | 38 | 12,405 | 503 sq mi (1,303 km2) |  |
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| Guthrie County | 077 | Guthrie Center | 39 | Jul 8, 1851 | Jackson County | Edwin B. Guthrie,Mexican–American War officer | 58 | 10,774 | 591 sq mi (1,531 km2) |  |
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| Hamilton County | 079 | Webster City | 40 | Dec 22, 1856 | Webster County | William W. Hamilton, President ofIowa Senate (1856–1857) | 36 | 14,856 | 577 sq mi (1,494 km2) |  |
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| Hancock County | 081 | Garner | 41 | Jan 15, 1851 | Wright County | John Hancock, President ofFirst Continental Congress | 16 | 10,616 | 571 sq mi (1,479 km2) |  |
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| Hardin County | 083 | Eldora | 42 | Jan 15, 1851 | Black Hawk County | John J. Hardin, prominent soldier,Black Hawk War | 37 | 16,464 | 569 sq mi (1,474 km2) |  |
|---|
| Harrison County | 085 | Logan | 43 | Jan 15, 1851 | Pottawattamie County | William Henry Harrison,US President | 55 | 14,626 | 697 sq mi (1,805 km2) |  |
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| Henry County | 087 | Mount Pleasant | 44 | Dec 7, 1836 | Wisconsin Territory | Disputed, see reference[15] | 88 | 19,361 | 434 sq mi (1,124 km2) |  |
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| Howard County | 089 | Cresco | 45 | Jan 15, 1851 | Chickasaw County | Tilghman Howard,US Representative from Indiana | 9 | 9,360 | 473 sq mi (1,225 km2) |  |
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| Humboldt County | 091 | Dakota City | 46 | Feb 26, 1857 | Webster County | Alexander von Humboldt,German scientist | 26 | 9,617 | 434 sq mi (1,124 km2) |  |
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| Ida County | 093 | Ida Grove | 47 | Jan 15, 1851 | Cherokee County | EitherMount Ida inGreece or Ida Smith, child of early settlers[16] | 32 | 6,810 | 432 sq mi (1,119 km2) |  |
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| Iowa County | 095 | Marengo | 48 | Feb 17, 1843 | Washington County | Iowa River that flows through the county | 63 | 16,423 | 586 sq mi (1,518 km2) |  |
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| Jackson County | 097 | Maquoketa | 49 | Dec 21, 1837 | Wisconsin Territory | Andrew Jackson,US President | 54 | 19,390 | 636 sq mi (1,647 km2) |  |
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| Jasper County | 099 | Newton | 50 | Jan 13, 1846 | Mahaska County | William Jasper,American Revolutionary War sergeant | 61 | 38,107 | 730 sq mi (1,891 km2) |  |
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| Jefferson County | 101 | Fairfield | 51 | Jan 21, 1839 | Native American lands | Thomas Jefferson,US President | 87 | 15,781 | 435 sq mi (1,127 km2) |  |
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| Johnson County | 103 | Iowa City | 52 | Dec 21, 1837 | Des Moines County, Iowa andWisconsin Territory | Richard Mentor Johnson,US Vice President; officially renamed afterLulu Johnson (1907-1995)[17] | 64 | 160,080 | 614 sq mi (1,590 km2) |  |
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| Jones County | 105 | Anamosa | 53 | Dec 21, 1837 | Wisconsin Territory | George Wallace Jones,Iowa Senator | 53 | 21,116 | 575 sq mi (1,489 km2) |  |
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| Keokuk County | 107 | Sigourney | 54 | Dec 21, 1837 | Washington County | Chief Keokuk | 74 | 9,855 | 579 sq mi (1,500 km2) |  |
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| Kossuth County | 109 | Algona | 55 | Jan 15, 1851 | Webster County | Lajos Kossuth,Hungarian revolutionary inspired by American democratic ideals | 5 | 14,408 | 973 sq mi (2,520 km2) |  |
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| Lee County | 111 | Fort Madison andKeokuk | 56 | Dec 7, 1836 | Des Moines County | William Elliott Lee, businessman from the New York Land Company, who sold the county's first tracts of land | 99 | 32,376 | 517 sq mi (1,339 km2) |  |
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| Linn County | 113 | Cedar Rapids | 57 | Dec 21, 1837 | Wisconsin Territory | Lewis Fields Linn, doctor andMissouri Senator | 52 | 231,762 | 718 sq mi (1,860 km2) |  |
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| Louisa County | 115 | Wapello | 58 | Dec 7, 1836 | Des Moines County | Disputed, see reference[18] | 76 | 10,630 | 402 sq mi (1,041 km2) |  |
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| Lucas County | 117 | Chariton | 59 | Jan 13, 1846 | Monroe County | Robert Lucas, firstGovernor ofIowa Territory | 84 | 8,758 | 431 sq mi (1,116 km2) |  |
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| Lyon County | 119 | Rock Rapids | 60 | Jan 15, 1851 | Woodbury County, Iowa | Nathaniel Lyon, first Union general to be killed in theAmerican Civil War, (formerly named Buncombe County) | 1 | 12,378 | 588 sq mi (1,523 km2) |  |
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| Madison County | 121 | Winterset | 61 | Jan 13, 1846 | Polk County | James Madison,US President | 70 | 17,161 | 561 sq mi (1,453 km2) |  |
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| Mahaska County | 123 | Oskaloosa | 62 | Feb 17, 1843 | Meskwaki andSaukIndian lands | Chief Mahaska | 73 | 22,034 | 571 sq mi (1,479 km2) |  |
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| Marion County | 125 | Knoxville | 63 | Jun 10, 1845 | Washington County | Francis Marion,American Revolutionary War general | 72 | 34,048 | 554 sq mi (1,435 km2) |  |
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| Marshall County | 127 | Marshalltown | 64 | Jan 13, 1846 | Jasper County | John Marshall,Chief Justice of the United States Supreme Court | 49 | 40,392 | 572 sq mi (1,481 km2) |  |
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| Mills County | 129 | Glenwood | 65 | Jan 15, 1851 | Pottawattamie County | Frederick Mills, major killed during theBattle of Churubusco,Mexican–American War | 79 | 14,717 | 437 sq mi (1,132 km2) |  |
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| Mitchell County | 131 | Osage | 66 | Jan 15, 1851 | Chickasaw County | John Mitchel,Irish revolutionary who operated out of the US | 8 | 10,632 | 469 sq mi (1,215 km2) |  |
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| Monona County | 133 | Onawa | 67 | Jan 15, 1851 | Harrison County | Probably from the name of a fictional Native American character in a play[14]: 295 | 43 | 8,429 | 693 sq mi (1,795 km2) |  |
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| Monroe County | 135 | Albia | 68 | Feb 17, 1843 | Wapello County | James Monroe,US President | 85 | 7,373 | 433 sq mi (1,121 km2) |  |
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| Montgomery County | 137 | Red Oak | 69 | Jan 15, 1851 | Polk County | Richard Montgomery,American Revolutionary War general | 80 | 10,063 | 424 sq mi (1,098 km2) |  |
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| Muscatine County | 139 | Muscatine | 70 | Dec 7, 1836 | Des Moines County | debated, possiblyMascouten People | 77 | 42,132 | 439 sq mi (1,137 km2) |  |
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| O'Brien County | 141 | Primghar | 71 | Jan 15, 1851 | Cherokee County | William Smith O'Brien, Irish revolutionary inspired by American democratic ideals | 13 | 14,260 | 573 sq mi (1,484 km2) |  |
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| Osceola County | 143 | Sibley | 72 | Jan 15, 1851 | Woodbury County | Osceola,Seminole leader | 2 | 6,036 | 399 sq mi (1,033 km2) |  |
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| Page County | 145 | Clarinda | 73 | Feb 24, 1847 | Pottawattamie County | John Page, officer killed inBattle of Palo Alto,Mexican–American War | 91 | 15,038 | 535 sq mi (1,386 km2) |  |
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| Palo Alto County | 147 | Emmetsburg | 74 | Jan 15, 1851 | Kossuth County | Battle of Palo Alto,Mexican–American War | 15 | 8,809 | 564 sq mi (1,461 km2) |  |
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| Plymouth County | 149 | Le Mars | 75 | Jan 15, 1851 | Woodbury County | Plymouth, Massachusetts | 22 | 25,825 | 864 sq mi (2,238 km2) |  |
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| Pocahontas County | 151 | Pocahontas | 76 | Jan 15, 1851 | Greene County andHumboldt County | Pocahontas, famous Native American woman | 25 | 7,006 | 578 sq mi (1,497 km2) |  |
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| Polk County | 153 | Des Moines | 77 | Jan 13, 1846 | Native American lands | James K. Polk,US President | 60 | 516,185 | 570 sq mi (1,476 km2) |  |
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| Pottawattamie County | 155 | Council Bluffs | 78 | Feb 24, 1847 | Native American lands | Potawatomi People | 67 | 93,529 | 954 sq mi (2,471 km2) |  |
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| Poweshiek County | 157 | Montezuma | 79 | Feb 17, 1843 | Meskwaki lands | Chief Poweshiek,Meskwaki | 62 | 18,454 | 585 sq mi (1,515 km2) |  |
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| Ringgold County | 159 | Mount Ayr | 80 | Feb 24, 1847 | Taylor County | Samuel Ringgold, major killed in theMexican–American War | 93 | 4,608 | 538 sq mi (1,393 km2) |  |
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| Sac County | 161 | Sac City | 81 | Jan 15, 1851 | Greene County | Sauk (Sac) People | 33 | 9,533 | 576 sq mi (1,492 km2) |  |
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| Scott County | 163 | Davenport | 82 | Dec 21, 1837 | Wisconsin Territory | Winfield Scott,War of 1812 General | 78 | 175,601 | 458 sq mi (1,186 km2) |  |
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| Shelby County | 165 | Harlan | 83 | Jan 15, 1851 | Cass County | Isaac Shelby,American Revolutionary War General,War of 1812 | 56 | 11,821 | 591 sq mi (1,531 km2) |  |
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| Sioux County | 167 | Orange City | 84 | Jan 15, 1851 | Plymouth County | Sioux People | 12 | 36,554 | 768 sq mi (1,989 km2) |  |
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| Story County | 169 | Nevada | 85 | Jan 13, 1846 | Boone County,Jasper County, andPolk County | Joseph Story,US Supreme Court Justice | 48 | 102,498 | 573 sq mi (1,484 km2) |  |
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| Tama County | 171 | Toledo | 86 | Feb 17, 1843 | Benton County andBoone County | Disputed, see reference[19] | 50 | 16,738 | 721 sq mi (1,867 km2) |  |
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| Taylor County | 173 | Bedford | 87 | Feb 24, 1847 | Page County | Zachary Taylor,US President | 92 | 5,825 | 534 sq mi (1,383 km2) |  |
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| Union County | 175 | Creston | 88 | Jan 15, 1851 | Clarke County | The union of the states | 82 | 11,955 | 424 sq mi (1,098 km2) |  |
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| Van Buren County | 177 | Keosauqua | 89 | Dec 7, 1836 | Des Moines County | Martin Van Buren,US President | 98 | 7,217 | 485 sq mi (1,256 km2) |  |
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| Wapello County | 179 | Ottumwa | 90 | Feb 17, 1843 | Native American lands | Chief Wapello | 86 | 35,681 | 432 sq mi (1,119 km2) |  |
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| Warren County | 181 | Indianola | 91 | Jan 13, 1846 | Polk County | Joseph Warren,American Revolutionary War General | 71 | 56,343 | 572 sq mi (1,481 km2) |  |
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| Washington County | 183 | Washington | 92 | Jan 25, 1839 | Wisconsin Territory | George Washington,US President | 75 | 22,631 | 569 sq mi (1,474 km2) |  |
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| Wayne County | 185 | Corydon | 93 | Jan 13, 1846 | Appanoose County | Anthony Wayne,American Revolutionary War General | 95 | 6,622 | 526 sq mi (1,362 km2) |  |
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| Webster County | 187 | Fort Dodge | 94 | Jan 12, 1853 | Risley County and Yell County (defunct IA counties)[20] | Daniel Webster,Massachusetts Senator | 35 | 36,909 | 715 sq mi (1,852 km2) |  |
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| Winnebago County | 189 | Forest City | 95 | Jan 15, 1851 | Kossuth County | Winnebago (Ho–Chunk) People | 6 | 10,383 | 400 sq mi (1,036 km2) |  |
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| Winneshiek County | 191 | Decorah | 96 | Feb 20, 1847 | Native American lands | Chief Winneshiek | 10 | 19,723 | 690 sq mi (1,787 km2) |  |
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| Woodbury County | 193 | Sioux City | 97 | Jan 12, 1853 | Wahkaw County (renamed),Polk County | Levi Woodbury,New Hampshire Governor | 31 | 107,257 | 873 sq mi (2,261 km2) |  |
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| Worth County | 195 | Northwood | 98 | Jan 15, 1851 | Mitchell County | William Jenkins Worth,Black Hawk War andMexican–American War officer | 7 | 7,307 | 400 sq mi (1,036 km2) |  |
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| Wright County | 197 | Clarion | 99 | Jan 15, 1851 | Webster County and Kossuth County | Silas Wright,New York Governor, andJoseph Albert Wright,Indiana Governor (brothers) | 27 | 12,729 | 581 sq mi (1,505 km2) |  |
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