Adair County	001	Greenfield	01	Jan 15, 1851	Cass County	John Adair, Kentucky Governor	69	7,682	569 sq mi
(1,474 km2)	State map highlighting Adair County
Adams County	003	Corning	02	Jan 15, 1851	Taylor County	John Adams, US President	81	4,029	424 sq mi
(1,098 km2)	State map highlighting Adams County
Allamakee County	005	Waukon	03	Feb 20, 1847	Clayton County	Disputed, possibly Allan Makee, early trader and guide for settlers	11	14,330	640 sq mi
(1,658 km2)	State map highlighting Allamakee County
Appanoose County	007	Centerville	04	Feb 17, 1843	Davis County	Chief Appanoose, headed peace party in the Black Hawk War	96	12,884	496 sq mi
(1,285 km2)	State map highlighting Appanoose County
Audubon County	009	Audubon	05	Jan 15, 1851	Black Hawk County and Cass County	John James Audubon, ornithologist and artist	57	6,119	443 sq mi
(1,147 km2)	State map highlighting Audubon County
Benton County	011	Vinton	06	Dec 21, 1837	Native American lands and Wisconsin Territory	Thomas Hart Benton, Missouri Senator	51	26,076	716 sq mi
(1,854 km2)	State map highlighting Benton County
Black Hawk County	013	Waterloo	07	Feb 17, 1843	Delaware County	Black Hawk, leader during Black Hawk War	39	131,090	567 sq mi
(1,469 km2)	State map highlighting Black Hawk County
Boone County	015	Boone	08	Jan 13, 1846	Polk County	Nathan Boone, one of the first to survey Iowa	47	26,306	572 sq mi
(1,481 km2)	State map highlighting Boone County
Bremer County	017	Waverly	09	Jan 15, 1851	Native American lands and Winnebago County	Fredrika Bremer, Swedish poet and author	30	24,276	428 sq mi
(1,109 km2)	State map highlighting Bremer County
Buchanan County	019	Independence	10	Dec 21, 1837	Delaware County and Wisconsin Territory	James Buchanan, US President	40	20,958	571 sq mi
(1,479 km2)	State map highlighting Buchanan County
Buena Vista County	021	Storm Lake	11	Jan 15, 1851	Clay County and Sac County	Battle of Buena Vista, Mexican.American War	24	20,260	575 sq mi
(1,489 km2)	State map highlighting Buena Vista County
Butler County	023	Allison	12	Jan 15, 1851	Black Hawk County and Buchanan County	William Orlando Butler, War of 1812 hero	29	14,867	580 sq mi
(1,502 km2)	State map highlighting Butler County
Calhoun County	025	Rockwell City	13	Jan 15, 1851	Fox County (renamed)	John C. Calhoun, US Vice President	34	9,670	570 sq mi
(1,476 km2)	State map highlighting Calhoun County
Carroll County	027	Carroll	14	Jan 15, 1851	Guthrie County	Charles Carroll, signatory of the Declaration of Independence	45	20,816	569 sq mi
(1,474 km2)	State map highlighting Carroll County
Cass County	029	Atlantic	15	Jan 15, 1851	Pottawattamie County	Lewis Cass, Michigan Senator	68	13,956	564 sq mi
(1,461 km2)	State map highlighting Cass County
Cedar County	031	Tipton	16	Dec 21, 1837	Wisconsin Territory	Cedar River that runs through county	65	18,499	580 sq mi
(1,502 km2)	State map highlighting Cedar County
Cerro Gordo County	033	Mason City	17	Jan 15, 1851	Floyd County	Battle of Cerro Gordo, Mexican.American War	17	44,151	568 sq mi
(1,471 km2)	State map highlighting Cerro Gordo County
Cherokee County	035	Cherokee	18	Jan 15, 1851	Crawford County	Cherokee People	23	12,072	577 sq mi
(1,494 km2)	State map highlighting Cherokee County
Chickasaw County	037	New Hampton	19	Jan 15, 1851	Fayette County	Chickasaw People	19	12,439	505 sq mi
(1,308 km2)	State map highlighting Chickasaw County
Clarke County	039	Osceola	20	Jan 13, 1846	Lucas County	James Clarke, Governor of Iowa Territory	83	9,286	431 sq mi
(1,116 km2)	State map highlighting Clarke County
Clay County	041	Spencer	21	Jan 15, 1851	Native American lands	Henry Clay, Jr., officer in the Mexican.American War	14	16,667	569 sq mi
(1,474 km2)	State map highlighting Clay County
Clayton County	043	Elkader	22	Dec 21, 1837	Dubuque County and Wisconsin Territory	John M. Clayton, Delaware Senator	21	18,129	779 sq mi
(2,018 km2)	State map highlighting Clayton County
Clinton County	045	Clinton	23	Dec 21, 1837	Dubuque County and Wisconsin Territory	DeWitt Clinton, New York Governor	66	49,116	695 sq mi
(1,800 km2)	State map highlighting Clinton County
Crawford County	047	Denison	24	Jan 15, 1851	Shelby County	William Harris Crawford, Georgia Senator	44	17,096	714 sq mi
(1,849 km2)	State map highlighting Crawford County
Dallas County	049	Adel	25	Jan 13, 1846	Polk County	George Mifflin Dallas, US Vice President	59	66,135	586 sq mi
(1,518 km2)	State map highlighting Dallas County
Davis County	051	Bloomfield	26	Feb 17, 1843	Van Buren County	Garrett Davis, Kentucky Congressman	97	8,753	503 sq mi
(1,303 km2)	State map highlighting Davis County
Decatur County	053	Leon	27	Jan 13, 1846	Appanoose County	Stephen Decatur, War of 1812 naval officer	94	8,457	532 sq mi
(1,378 km2)	State map highlighting Decatur County
Delaware County	055	Manchester	28	Dec 21, 1837	Dubuque County and Wisconsin Territory	State of Delaware, home of Iowa statehood advocate US Senator John M. Clayton	41	17,764	578 sq mi
(1,497 km2)	State map highlighting Delaware County
Des Moines County	057	Burlington	29	Sep 6, 1834	Michigan Territory and Wisconsin Territory	Des Moines River that once ran through the county	89	40,325	416 sq mi
(1,077 km2)	State map highlighting Des Moines County
Dickinson County	059	Spirit Lake	30	Jan 15, 1851	Kossuth County	Daniel Stevens Dickinson, New York Senator	3	16,667	381 sq mi
(987 km2)	State map highlighting Dickinson County
Dubuque County	061	Dubuque	31	Sep 6, 1834	Michigan Territory and Wisconsin Territory	Julien Dubuque, first permanent white settler in Iowa	42	93,653	608 sq mi
(1,575 km2)	State map highlighting Dubuque County
Emmet County	063	Estherville	32	Jan 15, 1851	Dickinson County and Kossuth County	Robert Emmet, Irish revolutionary and American republican sympathizer	4	10,302	396 sq mi
(1,026 km2)	State map highlighting Emmet County
Fayette County	065	West Union	33	Dec 21, 1837	Clayton County and Wisconsin Territory	Marquis de Lafayette, Frenchman who aided colonial forces during American Revolutionary War	20	20,880	731 sq mi
(1,893 km2)	State map highlighting Fayette County
Floyd County	067	Charles City	34	Jan 15, 1851	Chickasaw County	Charles Floyd, member of Lewis and Clark Expedition who died in Iowa	18	16,303	501 sq mi
(1,298 km2)	State map highlighting Floyd County
Franklin County	069	Hampton	35	Jan 15, 1851	Chickasaw County	Benjamin Franklin, statesman and US founding father	28	10,680	582 sq mi
(1,507 km2)	State map highlighting Franklin County
Fremont County	071	Sidney	36	Feb 24, 1847	Pottawattamie County	John Charles Fremont, Mexican.American War officer	90	7,441	511 sq mi
(1,323 km2)	State map highlighting Fremont County
Greene County	073	Jefferson	37	Jan 15, 1851	Dallas County	Nathanael Greene, American Revolutionary War general	46	9,336	568 sq mi
(1,471 km2)	State map highlighting Greene County
Grundy County	075	Grundy Center	38	Jan 15, 1851	Black Hawk County	Felix Grundy, Tennessee Congressman	38	12,453	503 sq mi
(1,303 km2)	State map highlighting Grundy County
Guthrie County	077	Guthrie Center	39	Jul 8, 1851	Jackson County	Edwin B. Guthrie, Mexican.American War officer	58	10,954	591 sq mi
(1,531 km2)	State map highlighting Guthrie County
Hamilton County	079	Webster City	40	Dec 22, 1856	Webster County	William W. Hamilton, President of Iowa Senate (1856.1857)	36	15,673	577 sq mi
(1,494 km2)	State map highlighting Hamilton County
Hancock County	081	Garner	41	Jan 15, 1851	Wright County	John Hancock, President of First Continental Congress	16	11,341	571 sq mi
(1,479 km2)	State map highlighting Hancock County
Hardin County	083	Eldora	42	Jan 15, 1851	Black Hawk County	John J. Hardin, prominent soldier, Black Hawk War	37	17,534	569 sq mi
(1,474 km2)	State map highlighting Hardin County
Harrison County	085	Logan	43	Jan 15, 1851	Pottawattamie County	William Henry Harrison, US President	55	14,928	697 sq mi
(1,805 km2)	State map highlighting Harrison County
Henry County	087	Mount Pleasant	44	Dec 7, 1836	Wisconsin Territory	Disputed, see reference[14]	88	20,145	434 sq mi
(1,124 km2)	State map highlighting Henry County
Howard County	089	Cresco	45	Jan 15, 1851	Chickasaw County	Tilghman Howard, US Representative from Indiana	9	9,566	473 sq mi
(1,225 km2)	State map highlighting Howard County
Humboldt County	091	Dakota City	46	Feb 26, 1857	Webster County	Alexander von Humboldt, German scientist	26	9,815	434 sq mi
(1,124 km2)	State map highlighting Humboldt County
Ida County	093	Ida Grove	47	Jan 15, 1851	Cherokee County	Mount Ida in Greece	32	7,089	432 sq mi
(1,119 km2)	State map highlighting Ida County
Iowa County	095	Marengo	48	Feb 17, 1843	Washington County	Iowa River that flows through the county	63	16,355	586 sq mi
(1,518 km2)	State map highlighting Iowa County
Jackson County	097	Maquoketa	49	Dec 21, 1837	Wisconsin Territory	Andrew Jackson, US President	54	19,848	636 sq mi
(1,647 km2)	State map highlighting Jackson County
Jasper County	099	Newton	50	Jan 13, 1846	Mahaska County	William Jasper, American Revolutionary War sergeant	61	36,842	730 sq mi
(1,891 km2)	State map highlighting Jasper County
Jefferson County	101	Fairfield	51	Jan 21, 1839	Native American lands	Thomas Jefferson, US President	87	16,843	435 sq mi
(1,127 km2)	State map highlighting Jefferson County
Johnson County	103	Iowa City	52	Dec 21, 1837	Des Moines County, Iowa and Wisconsin Territory	Richard Mentor Johnson, US Vice President	64	130,882	614 sq mi
(1,590 km2)	State map highlighting Johnson County
Jones County	105	Anamosa	53	Dec 21, 1837	Wisconsin Territory	George Wallace Jones, Iowa Senator	53	20,638	575 sq mi
(1,489 km2)	State map highlighting Jones County
Keokuk County	107	Sigourney	54	Dec 21, 1837	Washington County	Chief Keokuk	74	10,511	579 sq mi
(1,500 km2)	State map highlighting Keokuk County
Kossuth County	109	Algona	55	Jan 15, 1851	Webster County	Lajos Kossuth, Hungarian revolutionary inspired by American democratic ideals	5	15,543	973 sq mi
(2,520 km2)	State map highlighting Kossuth County
Lee County	111	Fort Madison and Keokuk	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	35,862	517 sq mi
(1,339 km2)	State map highlighting Lee County
Linn County	113	Cedar Rapids	57	Dec 21, 1837	Wisconsin Territory	Lewis Fields Linn, doctor and Missouri Senator	52	211,226	718 sq mi
(1,860 km2)	State map highlighting Linn County
Louisa County	115	Wapello	58	Dec 7, 1836	Des Moines County	Disputed, see reference[15]	76	11,387	402 sq mi
(1,041 km2)	State map highlighting Louisa County
Lucas County	117	Chariton	59	Jan 13, 1846	Monroe County	Robert Lucas, first Governor of Iowa Territory	84	8,898	431 sq mi
(1,116 km2)	State map highlighting Lucas County
Lyon County	119	Rock Rapids	60	Jan 15, 1851	Woodbury County, Iowa	Nathaniel Lyon, first Union general to be killed in the American Civil War, (formerly named Buncombe County)	1	11,581	588 sq mi
(1,523 km2)	State map highlighting Lyon County
Madison County	121	Winterset	61	Jan 13, 1846	Polk County	James Madison, US President	70	15,679	561 sq mi
(1,453 km2)	State map highlighting Madison County
Mahaska County	123	Oskaloosa	62	Feb 17, 1843	Fox and Sac Indian lands	Chief Mahaska	73	22,381	571 sq mi
(1,479 km2)	State map highlighting Mahaska County
Marion County	125	Knoxville	63	Jun 10, 1845	Washington County	Francis Marion, American Revolutionary War general	72	33,309	554 sq mi
(1,435 km2)	State map highlighting Marion County
Marshall County	127	Marshalltown	64	Jan 13, 1846	Jasper County	John Marshall, Chief Justice of the United States Supreme Court	49	40,648	572 sq mi
(1,481 km2)	State map highlighting Marshall County
Mills County	129	Glenwood	65	Jan 15, 1851	Pottawattamie County	Frederick Mills, major killed during the Battle of Churubusco, Mexican.American War	79	15,059	437 sq mi
(1,132 km2)	State map highlighting Mills County
Mitchell County	131	Osage	66	Jan 15, 1851	Chickasaw County	John Mitchel, Irish revolutionary who operated out of the US	8	10,776	469 sq mi
(1,215 km2)	State map highlighting Mitchell County
Monona County	133	Onawa	67	Jan 15, 1851	Harrison County	Native American word thought to mean "peaceful valley"	43	9,243	693 sq mi
(1,795 km2)	State map highlighting Monona County
Monroe County	135	Albia	68	Feb 17, 1843	Wapello County	James Monroe, US President	85	7,970	433 sq mi
(1,121 km2)	State map highlighting Monroe County
Montgomery County	137	Red Oak	69	Jan 15, 1851	Polk County	Richard Montgomery, American Revolutionary War general	80	10,740	424 sq mi
(1,098 km2)	State map highlighting Montgomery County
Muscatine County	139	Muscatine	70	Dec 7, 1836	Des Moines County	debated, possibly Mascouten People	77	42,745	439 sq mi
(1,137 km2)	State map highlighting Muscatine County
O'Brien County	141	Primghar	71	Jan 15, 1851	Cherokee County	William Smith O'Brien, Irish revolutionary inspired by American democratic ideals	13	14,398	573 sq mi
(1,484 km2)	State map highlighting O'Brien County
Osceola County	143	Sibley	72	Jan 15, 1851	Woodbury County	Osceola, Seminole leader	2	6,462	399 sq mi
(1,033 km2)	State map highlighting Osceola County
Page County	145	Clarinda	73	Feb 24, 1847	Pottawattamie County	John Page, officer killed in Battle of Palo Alto, Mexican.American War	91	15,932	535 sq mi
(1,386 km2)	State map highlighting Page County
Palo Alto County	147	Emmetsburg	74	Jan 15, 1851	Kossuth County	Battle of Palo Alto, Mexican.American War	15	9,421	564 sq mi
(1,461 km2)	State map highlighting Palo Alto County
Plymouth County	149	Le Mars	75	Jan 15, 1851	Woodbury County	Plymouth, Massachusetts	22	24,986	864 sq mi
(2,238 km2)	State map highlighting Plymouth County
Pocahontas County	151	Pocahontas	76	Jan 15, 1851	Greene County and Humboldt County	Pocahontas, famous Native American woman	25	7,310	578 sq mi
(1,497 km2)	State map highlighting Pocahontas County
Polk County	153	Des Moines	77	January 13, 1846	Native American lands	James K. Polk, US President	60	430,640	570 sq mi
(1,476 km2)	State map highlighting Polk County
Pottawattamie County	155	Council Bluffs	78	Feb 24, 1847	Native American lands	Potawatomi People	67	93,158	954 sq mi
(2,471 km2)	State map highlighting Pottawattamie County
Poweshiek County	157	Montezuma	79	Feb 17, 1843	Meskwaki lands	Chief Poweshiek, Meskwaki	62	18,914	585 sq mi
(1,515 km2)	State map highlighting Poweshiek County
Ringgold County	159	Mount Ayr	80	Feb 24, 1847	Taylor County	Samuel Ringgold, major killed in the Mexican.American War	93	5,131	538 sq mi
(1,393 km2)	State map highlighting Ringgold County
Sac County	161	Sac City	81	Jan 15, 1851	Greene County	Sauk (Sac) People	33	10,350	576 sq mi
(1,492 km2)	State map highlighting Sac County
Scott County	163	Davenport	82	Dec 21, 1837	Wisconsin Territory	Winfield Scott, War of 1812 General	78	165,224	458 sq mi
(1,186 km2)	State map highlighting Scott County
Shelby County	165	Harlan	83	Jan 15, 1851	Cass County	Isaac Shelby, American Revolutionary War General, War of 1812	56	12,167	591 sq mi
(1,531 km2)	State map highlighting Shelby County
Sioux County	167	Orange City	84	Jan 15, 1851	Plymouth County	Sioux People	12	33,704	768 sq mi
(1,989 km2)	State map highlighting Sioux County
Story County	169	Nevada	85	Jan 13, 1846	Boone County, Jasper County, and Polk County	Joseph Story, US Supreme Court Justice	48	89,542	573 sq mi
(1,484 km2)	State map highlighting Story County
Tama County	171	Toledo	86	Feb 17, 1843	Benton County and Boone County	Disputed, see reference[16]	50	17,767	721 sq mi
(1,867 km2)	State map highlighting Tama County
Taylor County	173	Bedford	87	February 24, 1847	Page County	Zachary Taylor, US President	92	6,317	534 sq mi
(1,383 km2)	State map highlighting Taylor County
Union County	175	Creston	88	Jan 15, 1851	Clarke County	The union of the states	82	12,534	424 sq mi
(1,098 km2)	State map highlighting Union County
Van Buren County	177	Keosauqua	89	Dec 7, 1836	Des Moines County	Martin Van Buren, US President	98	7,570	485 sq mi
(1,256 km2)	State map highlighting Van Buren County
Wapello County	179	Ottumwa	90	Feb 17, 1843	Native American lands	Chief Wapello	86	35,625	432 sq mi
(1,119 km2)	State map highlighting Wapello County
Warren County	181	Indianola	91	Jan 13, 1846	Polk County	Joseph Warren, American Revolutionary War General	71	46,225	572 sq mi
(1,481 km2)	State map highlighting Warren County
Washington County	183	Washington	92	Jan 25, 1839	Wisconsin Territory	George Washington, US President	75	21,704	569 sq mi
(1,474 km2)	State map highlighting Washington County
Wayne County	185	Corydon	93	Jan 13, 1846	Appanoose County	Anthony Wayne, American Revolutionary War General	95	6,403	526 sq mi
(1,362 km2)	State map highlighting Wayne County
Webster County	187	Fort Dodge	94	Jan 12, 1853	Risley County and Yell County (defunct IA counties)[17]	Daniel Webster, Massachusetts Senator	35	38,013	715 sq mi
(1,852 km2)	State map highlighting Webster County
Winnebago County	189	Forest City	95	Jan 15, 1851	Kossuth County	Winnebago (Ho.Chunk) People	6	10,866	400 sq mi
(1,036 km2)	State map highlighting Winnebago County
Winneshiek County	191	Decorah	96	Feb 20, 1847	Native American lands	Chief Winneshiek	10	21,056	690 sq mi
(1,787 km2)	State map highlighting Winneshiek County
Woodbury County	193	Sioux City	97	Jan 12, 1853	Wahkaw County (renamed), Polk County	Levi Woodbury, New Hampshire Governor	31	102,172	873 sq mi
(2,261 km2)	State map highlighting Woodbury County
Worth County	195	Northwood	98	Jan 15, 1851	Mitchell County	William Jenkins Worth, Black Hawk War and Mexican.American War officer	7	7,598	400 sq mi
(1,036 km2)	State map highlighting Worth County
Wright County	197	Clarion	99	Jan 15, 1851	Webster County and Kossuth County	Silas Wright, New York Governor, and Joseph Albert Wright, Indiana Governor (brothers)	27	13,229	581 sq mi
(1,505 km2)	State map highlighting Wright County