List of counties in Illinois

Counties of Illinois
JD SN WI ↑ BN MH LK CK WL DP KA KE DK LE OG CR WS ←RI MR HE BU PM ML LS GY KK IQ FD LV WF PE ST KX WR HD HK MU SR FN MS TZ ME LO DW MC PT CH VE ED DG CO MT SH CN SA MD CS BR AD PK MG SC GR CA→ JY MP MY MI BD FA EF CD CL JA CF LA RH CY MN CT CI MO RA WA JE WN ES ←WB WH HM FK PY JK WM SL GA ←HA PO JN UN AL→ PU MA
Location	State of Illinois
Number	102
Populations	3,569 (Hardin) – 5,087,072 (Cook)
Areas	172 square miles (450 km2) (Putnam) – 1,186 square miles (3,070 km2) (McLean)
Government	County government
Subdivisions	261 Precincts 1,433 Townships

There are 102 counties in Illinois. The most populous of these is Cook County, the second-most populous county in the United States and the home of Chicago, while the least populous is Hardin County. The largest by land area is McLean County, while the smallest is Putnam County. Illinois's FIPS state code is 17 and its postal abbreviation is IL.

What is now Illinois was claimed as part of Illinois County, Virginia, between 1778 and 1782. Modern-day county formation dates to 1790 when the area was part of the Northwest Territory; two counties—St. Clair and Knox—were created at that time. Knox would later become a county in Indiana and is unrelated to the current Knox County in Illinois, while St. Clair would become the oldest county in Illinois. 15 counties had been created by the time Illinois achieved statehood in 1818. The last county, Ford County, was created in 1859. Cook County, established in 1831 and named for the early Illinois Attorney General Daniel Pope Cook, contained the absolute majority of the state's population in the first half of the 20th century and retains more than 40% of it as of the 2020 census^[update].

Most counties in Illinois were named after early American leaders, especially of the American Revolutionary War, as well as soldiers from the Battle of Tippecanoe and the War of 1812. Some are named after natural features or counties in other states. Some are named for early Illinois leaders. Two counties are named for Native American tribes, and one bears the name of a plant used as a food source by Native Americans. While it does have a Lincoln city, Illinois does not have a county named after its favorite son, Abraham Lincoln; it does, however, have a Douglas County (founded 1859) named after his political rival Stephen A. Douglas. It also has Calhoun County (founded 1825), named after John C. Calhoun, outspoken for his pro-slavery and pro-southern views in the years preceding the American Civil War. Several of the counties are named after Southerners, reflecting the fact that Illinois was for a short time part of Virginia, and settled in its early years by many Southerners. No counties are named after heroes of the Civil War, mainly because the counties were all named before that war. The state does have a Lee County (founded 1839) named after Henry Lee III, the father of Robert E. Lee, who at one time served in Illinois. Illinois also has two counties named after the same person, New York governor DeWitt Clinton (DeWitt County, and Clinton County).

Information on the FIPS county code, county seat, year of establishment, origin, etymology, population, area and map of each county is included in the table below.

Note: the links in the FIPS County Code column are to the United States Census Bureau page for that county.

County	FIPS code[1]	County seat[2]	Est.[2]	Origin	Etymology[3][4]	Population[5]	Area[2]	Map
Adams County	001	Quincy	1825	Pike County	John Quincy Adams (1767–1848), sixth President of the United States	64,441	855 sq mi (2,214 km2)
Alexander County	003	Cairo	1819	Union County	William M. Alexander, settler and state representative in the Illinois General Assembly	4,695	236 sq mi (611 km2)
Bond County	005	Greenville	1817	Crawford County, Edwards County, and Madison County	Shadrach Bond (1773–1832), first Governor of Illinois	16,450	380 sq mi (984 km2)
Boone County	007	Belvidere	1837	Winnebago County	Daniel Boone (1734–1820), trailblazer of the Wilderness Road in Kentucky	53,202	280 sq mi (725 km2)
Brown County	009	Mount Sterling	1839	Schuyler County	Jacob Brown (1775–1828), successful War of 1812 army officer responsible for Great Lakes defenses	6,294	305 sq mi (790 km2)
Bureau County	011	Princeton	1837	Putnam County	Pierre de Bureo, Frenchman, North American fur trader	32,729	869 sq mi (2,251 km2)
Calhoun County	013	Hardin	1825	Pike County	John C. Calhoun (1782–1850), South Carolina senator and seventh Vice President of the United States	4,317	253 sq mi (655 km2)
Carroll County	015	Mount Carroll	1839	Jo Daviess	Charles Carroll of Carrollton (1737–1832), signed the Declaration of Independence on behalf of Maryland	15,526	445 sq mi (1,153 km2)
Cass County	017	Virginia	1837	Morgan County	Lewis Cass (1782–1866), second governor of Michigan Territory, fourteenth United States Secretary of War	12,596	375 sq mi (971 km2)
Champaign County	019	Urbana	1833	Vermilion County	Champaign County, Ohio, which took its name from the French for "open level country"	205,644	996 sq mi (2,580 km2)
Christian County	021	Taylorville	1839	Sangamon County	Christian County, Kentucky, which was named after William Christian	33,228	709 sq mi (1,836 km2)
Clark County	023	Marshall	1819	Crawford County	George Rogers Clark (1752–1818), highest-ranking officer in the Northwest Territory during the American Revolution	15,088	501 sq mi (1,298 km2)
Clay County	025	Louisville	1824	Wayne, Lawrence, Fayette, and Crawford County	Henry Clay (1777–1852), Kentucky legislator who negotiated the Missouri Compromise	12,999	468 sq mi (1,212 km2)
Clinton County	027	Carlyle	1824	Washington, Bond, and Fayette County	DeWitt Clinton (1769–1828), Governor of New York, responsible for the construction of the Erie Canal	36,785	474 sq mi (1,228 km2)
Coles County	029	Charleston	1830	Clark and Edgar County	Edward Coles (1786–1868), second Governor of Illinois, responsible for the abolition of slavery in Illinois	46,060	508 sq mi (1,316 km2)
Cook County	031	Chicago	1831	Putnam County	Daniel Pope Cook (1794–1827), politician and first Attorney General of Illinois	5,087,072	944 sq mi (2,445 km2)
Crawford County	033	Robinson	1816	Edwards County	William H. Crawford (1772–1834), ninth United States Secretary of War, seventh Secretary of the Treasury	18,300	443 sq mi (1,147 km2)
Cumberland County	035	Toledo	1843	Coles County	Disputed: Cumberland Road, which entered the county; Cumberland, Maryland; or Cumberland River in Kentucky	10,261	345 sq mi (894 km2)
DeKalb County	037	Sycamore	1837	Kane County	Johann de Kalb (1721–1780), German officer in the Continental Army who fought alongside Gilbert du Motier, marquis de Lafayette	100,288	631 sq mi (1,634 km2)
DeWitt County	039	Clinton	1839	Macon and McLean County	DeWitt Clinton (1769–1828), Governor of New York, responsible for the construction of the Erie Canal	15,365	397 sq mi (1,028 km2)
Douglas County	041	Tuscola	1859	Coles County	Stephen A. Douglas (1813–1861), prominent Illinois Democrat who engaged in debates with Abraham Lincoln	19,629	416 sq mi (1,077 km2)
DuPage County	043	Wheaton	1839	Cook County	DuPage River	921,213	327 sq mi (847 km2)
Edgar County	045	Paris	1823	Clark County	John Edgar (c. 1750–1832), Illinois delegate to the Northwest Territory legislature; at the time, wealthiest man in Illinois	16,334	623 sq mi (1,614 km2)
Edwards County	047	Albion	1814	Gallatin County and Madison County	Ninian Edwards (1775–1833), third Governor of the State of Illinois and only governor of the Illinois Territory	5,968	222 sq mi (575 km2)
Effingham County	049	Effingham	1831	Fayette and Crawford County	Thomas Howard, 3rd Earl of Effingham, military officer who resigned from the British Army to avoid fighting the American colonies	34,331	478 sq mi (1,238 km2)
Fayette County	051	Vandalia	1821	Bond, Wayne, Clark, Jefferson, and Crawford County	Gilbert du Motier, marquis de Lafayette (1757–1834), French military officer who was a key factor in the American and French Revolutions.	21,164	716 sq mi (1,854 km2)
Ford County	053	Paxton	1859	Vermilion County	Thomas Ford (1800–1850), eighth Governor of Illinois; served during the Illinois Mormon War	13,250	485 sq mi (1,256 km2)
Franklin County	055	Benton	1818	White County and Gallatin County	Benjamin Franklin (1706–1790), prolific writer, inventor, and politician; key factor in the American Revolution	37,138	408 sq mi (1,057 km2)
Fulton County	057	Lewistown	1823	Pike County	Robert Fulton (1765–1815), inventor of the steamboat	32,541	865 sq mi (2,240 km2)
Gallatin County	059	Shawneetown	1812	Randolph County	Albert Gallatin (1761–1849), fourth and longest-serving United States Secretary of the Treasury	4,670	322 sq mi (834 km2)
Greene County	061	Carrollton	1821	Madison County	Nathanael Greene (1742–1786), major general in the Continental Army	11,543	543 sq mi (1,406 km2)
Grundy County	063	Morris	1841	LaSalle County	Felix Grundy (1777–1840), Tennessean senator who served as the thirteenth United States Attorney General	53,578	418 sq mi (1,083 km2)
Hamilton County	065	McLeansboro	1821	White County	Alexander Hamilton (1755–1804), first United States Secretary of the Treasury	7,911	434 sq mi (1,124 km2)
Hancock County	067	Carthage	1825	Adams County	John Hancock (1737–1793), first governor of the Massachusetts colony and president of the Second Continental Congress	17,186	793 sq mi (2,054 km2)
Hardin County	069	Elizabethtown	1839	Pope County	Hardin County, Kentucky, which was named after John Hardin	3,569	177 sq mi (458 km2)
Henderson County	071	Oquawka	1841	Warren County	Henderson County, Kentucky, which was named after Richard Henderson	6,088	378 sq mi (979 km2)
Henry County	073	Cambridge	1825	Fulton County	Patrick Henry (1736–1799), American Revolutionary War figure; first and sixth Governor of Virginia	48,448	822 sq mi (2,129 km2)
Iroquois County	075	Watseka	1833	Vermilion County	Iroquois Native Americans	26,136	1,117 sq mi (2,893 km2)
Jackson County	077	Murphysboro	1816	Randolph County and Johnson County	Andrew Jackson (1767–1845), seventh President of the United States, United States Senator from Tennessee, and general in the War of 1812	52,141	584 sq mi (1,513 km2)
Jasper County	079	Newton	1831	Clay and Crawford County	Sgt. William Jasper (c. 1750–1779), American Revolutionary War soldier popularized by Parson Weems	9,144	494 sq mi (1,279 km2)
Jefferson County	081	Mount Vernon	1819	Edwards and White County	Thomas Jefferson (1743–1826), third President of the United States, second Vice President of the United States, Governor of Virginia, and one of the foremost Founding Fathers of the United States	36,320	571 sq mi (1,479 km2)
Jersey County	083	Jerseyville	1839	Greene County	State of New Jersey, from which many early settlers hailed	21,091	369 sq mi (956 km2)
Jo Daviess County	085	Galena	1827	Henry, Mercer, and Putnam County	Joseph Hamilton Daveiss (1774–1811), commander of the Indiana Dragoons at the Battle of Tippecanoe	21,756	600 sq mi (1,554 km2)
Johnson County	087	Vienna	1812	Randolph County	Richard Mentor Johnson (c. 1780–1850), ninth Vice President of the United States and United States Senator from Kentucky	13,326	343 sq mi (888 km2)
Kane County	089	Geneva	1836	LaSalle County	Elias Kane (1794–1835), United States Senator from Illinois	514,982	519 sq mi (1,344 km2)
Kankakee County	091	Kankakee	1853	Iroquois and Will County	Kankakee River	105,940	676 sq mi (1,751 km2)
Kendall County	093	Yorkville	1841	LaSalle and Kane County	Amos Kendall (1789–1869), United States Postmaster General under Presidents Andrew Jackson and Martin Van Buren	139,976	320 sq mi (829 km2)
Knox County	095	Galesburg	1825	Fulton County	Gen. Henry Knox (1750–1806), American Revolutionary War general and first United States Secretary of War	48,411	716 sq mi (1,854 km2)
Lake County	097	Waukegan	1839	McHenry County	Lake Michigan	708,760	443 sq mi (1,147 km2)
LaSalle County	099	Ottawa	1831	Putnam and Tazewell County	Sieur de la Salle (1643–1687), French explorer of the Great Lakes	108,309	1,135 sq mi (2,940 km2)
Lawrence County	101	Lawrenceville	1821	Crawford and Edwards County	Capt. James Lawrence (1781–1813), commander of the USS Chesapeake in the War of 1812. Famous for his command "Don't give up the ship!"	14,813	372 sq mi (963 km2)
Lee County	103	Dixon	1839	Ogle County	"Light Horse" Henry Lee III (1756–1818), American Revolutionary War officer and ninth Governor of Virginia	33,654	724 sq mi (1,875 km2)
Livingston County	105	Pontiac	1837	LaSalle and McLean County	Edward Livingston (1764–1836), prominent jurist, Congressman from New York and Louisiana, and U.S. Secretary of State from 1831-33	35,320	1,043 sq mi (2,701 km2)
Logan County	107	Lincoln	1839	Sangamon County	John Logan, country doctor and early settler, and the father of John A. Logan	27,590	618 sq mi (1,601 km2)
Macon County	115	Decatur	1829	Shelby County	Nathaniel Macon (1758–1837), sixth Speaker of the United States House of Representatives and United States Senator from North Carolina	100,591	580 sq mi (1,502 km2)
Macoupin County	117	Carlinville	1829	Greene County	Native American word macoupin, meaning "American lotus"	44,018	862 sq mi (2,233 km2)
Madison County	119	Edwardsville	1812	St. Clair County and Randolph County	James Madison (1751–1836), fourth President of the United States and principal author of the Constitution of the United States	262,752	716 sq mi (1,854 km2)
Marion County	121	Salem	1823	Fayette and Jefferson County	Francis Marion (c. 1732–1795), general in the American Revolutionary War known as "The Swamp Fox"	36,673	572 sq mi (1,481 km2)
Marshall County	123	Lacon	1839	Putnam County	John Marshall (1755–1835), fourth and longest-serving Chief Justice of the United States, wrote opinion in Marbury v. Madison establishing the principle of judicial review	11,683	386 sq mi (1,000 km2)
Mason County	125	Havana	1841	Tazewell and Menard County	Named after Mason County, Kentucky, itself named after George Mason	12,523	539 sq mi (1,396 km2)
Massac County	127	Metropolis	1843	Pope and Johnson County	Fort Massac, a colonial-era fort on the Ohio River	13,661	237 sq mi (614 km2)
McDonough County	109	Macomb	1826	Schuyler County	Commodore Thomas Macdonough (1783–1825), commander of American naval forces at the Battle of Plattsburgh	26,839	589 sq mi (1,526 km2)
McHenry County	111	Woodstock	1836	Cook and LaSalle County	Major William McHenry (c. 1771–1835), officer during several campaigns against Native Americans and was a member of the Illinois legislature	312,800	603 sq mi (1,562 km2)
McLean County	113	Bloomington	1830	Tazewell County	John McLean (1791–1830), United States Representative and United States Senator from Illinois (the latter from 1824–25 and 1829–30)	170,441	1,183 sq mi (3,064 km2)
Menard County	129	Petersburg	1839	Sangamon County	Pierre Menard (1766–1844), prominent early settler and first Lieutenant Governor of Illinois	11,954	314 sq mi (813 km2)
Mercer County	131	Aledo	1825	Schuyler County	Hugh Mercer (1726–1777), British officer in the Seven Years' War and general in the Continental Army during the American Revolutionary War	15,487	561 sq mi (1,453 km2)
Monroe County	133	Waterloo	1816	Randolph County and St. Clair County	James Monroe (1758–1831), seventh United States Secretary of State, eighth United States Secretary of War, Governor of Virginia, and fifth President of the United States	34,957	385 sq mi (997 km2)
Montgomery County	135	Hillsboro	1821	Bond and Madison County	Gen. Richard Montgomery (1738–1775), brigadier-general in the Continental Army who led the unsuccessful invasion of Canada	27,663	703 sq mi (1,821 km2)
Morgan County	137	Jacksonville	1823	Sangamon County	Gen. Daniel Morgan (1736–1802), successful tactician in the American Revolutionary War and later United States Representative from Virginia	32,140	568 sq mi (1,471 km2)
Moultrie County	139	Sullivan	1843	Shelby and Macon County	Gen. William Moultrie (1730–1805), American Revolutionary War general and Governor of South Carolina	14,342	335 sq mi (868 km2)
Ogle County	141	Oregon	1836	Jo Daviess	Joseph Ogle (1737–1821), early settler in southwest Illinois, who helped found the first Methodist church in Illinois	51,265	758 sq mi (1,963 km2)
Peoria County	143	Peoria	1825	Fulton County	The Peoria Native American tribe	177,513	618 sq mi (1,601 km2)
Perry County	145	Pinckneyville	1827	Randolph and Jackson County	Cmdre. Oliver Hazard Perry (1785–1819), American naval officer who led the victorious American forces at the Battle of Lake Erie	20,503	441 sq mi (1,142 km2)
Piatt County	147	Monticello	1841	DeWitt and Macon County	James A. Piatt, the patriarch of a prominent settler family in the early history of the county	16,714	439 sq mi (1,137 km2)
Pike County	149	Pittsfield	1821	Madison, Bond, and Clark County	Zebulon Pike (1779–1813), early explorer of the American Southwest, namesake of Pikes Peak	14,342	831 sq mi (2,152 km2)
Pope County	151	Golconda	1816	Gallatin and Johnson County	Nathaniel Pope (1784–1850), early Delegate from Illinois Territory to Congress and judge on the United States District Court for the District of Illinois	3,707	368 sq mi (953 km2)
Pulaski County	153	Mound City	1843	Alexander and Johnson County	Gen. Casimir Pulaski (1745–1779), Polish American general of cavalry in the American Revolutionary War	4,911	199 sq mi (515 km2)
Putnam County	155	Hennepin	1825	Fulton County	Gen. Israel Putnam (1718–1790), commander of American forces at the Battle of Bunker Hill	5,561	160 sq mi (414 km2)
Randolph County	157	Chester	1795	St. Clair County	Edmund Randolph (1753–1813), first Attorney General of the United States, and briefly United States Secretary of State	29,815	575 sq mi (1,489 km2)
Richland County	159	Olney	1841	Clay and Lawrence County	Richland County, Ohio, itself named for its rich soil	15,488	360 sq mi (932 km2)
Rock Island County	161	Rock Island	1831	Jo Daviess County	Rock Island	141,236	427 sq mi (1,106 km2)
Saline County	165	Harrisburg	1847	Gallatin County	The Saline River and salt springs in the county	22,873	379 sq mi (982 km2)
Sangamon County	167	Springfield	1821	Madison and Bond County	Sangamon River	193,491	868 sq mi (2,248 km2)
Schuyler County	169	Rushville	1825	Pike and Fulton County	Gen. Philip Schuyler (1733–1804), American Revolutionary War general and United States Senator from New York	6,733	437 sq mi (1,132 km2)
Scott County	171	Winchester	1839	Morgan County	Scott County, Kentucky, itself named after Charles Scott	4,710	250 sq mi (647 km2)
Shelby County	173	Shelbyville	1827	Fayette County	Isaac Shelby (1750–1826), soldier in the American Revolutionary War and War of 1812; first and fifth Governor of Kentucky	20,568	758 sq mi (1,963 km2)
St. Clair County	163	Belleville	1790	original two counties	Arthur St. Clair (1737–1818), major general in the American Revolutionary War and first Governor of the Northwest Territory	251,018	657 sq mi (1,702 km2)
Stark County	175	Toulon	1839	Knox and Putnam County	Gen. John Stark (1728–1822), general in the American Revolutionary War, called the "Hero of Bennington"	5,218	288 sq mi (746 km2)
Stephenson County	177	Freeport	1837	Jo Daviess and Winnebago County	Benjamin Stephenson (1769–1822), representative of Illinois Territory in the United States Congress from 1814 to 1816	43,105	564 sq mi (1,461 km2)
Tazewell County	179	Pekin	1827	Sangamon County	Littleton Waller Tazewell (1774–1860), United States Senator from (and later governor of) Virginia	129,541	646 sq mi (1,673 km2)
Union County	181	Jonesboro	1818	Johnson County	The union of the United States	16,667	413 sq mi (1,070 km2)
Vermilion County	183	Danville	1826	Edgar County	The Vermilion River	71,652	898 sq mi (2,326 km2)
Wabash County	185	Mount Carmel	1824	Edwards County	The Wabash River	10,942	223 sq mi (578 km2)
Warren County	187	Monmouth	1825	Schuyler County	Joseph Warren (1741–1775), played a role in American Patriot movements, a prominent early fatality in the American Revolutionary War	16,185	542 sq mi (1,404 km2)
Washington County	189	Nashville	1818	St. Clair County	George Washington (1732–1799), commander-in-chief of American forces in the American Revolutionary War and first President of the United States	13,536	562 sq mi (1,456 km2)
Wayne County	191	Fairfield	1819	Edwards County	Gen. "Mad" Anthony Wayne (1745–1796), major general in the United States Army in the American Revolutionary War and the Northwest Indian War	15,761	713 sq mi (1,847 km2)
White County	193	Carmi	1815	Gallatin County	Isaac White (1776–1811), resident of Illinois who enlisted in the Indiana militia and was killed at the Battle of Tippecanoe	13,401	494 sq mi (1,279 km2)
Whiteside County	195	Morrison	1836	Jo Daviess and Henry County	Samuel Whiteside (1783–1868), state legislator and militia leader	54,498	684 sq mi (1,772 km2)
Will County	197	Joliet	1836	Cook and Iroquois County	Conrad Will (1779–1835),[6] physician, local businessman and longtime member of the state legislature	700,728	835 sq mi (2,163 km2)
Williamson County	199	Marion	1839	Franklin County	Williamson County, Tennessee, which was named for Hugh Williamson	66,706	420 sq mi (1,088 km2)
Winnebago County	201	Rockford	1836	Jo Daviess County	Winnebago Native Americans	280,922	513 sq mi (1,329 km2)
Woodford County	203	Eureka	1841	Tazewell and McLean County	Woodford County, Kentucky, which was named for William Woodford	38,285	527 sq mi (1,365 km2)

• Dane County was renamed in 1840 to the current Christian County.
• The original Knox County, Illinois, became extinct with the formation of the Illinois Territory in 1809 - or, more precisely, it became Knox County, Indiana. The modern Knox County, Illinois was formed much later and was not a part of the original Knox County.

• List of census-designated places in Illinois
• List of cities in Illinois
• List of Illinois townships
• List of precincts in Illinois
• List of towns and villages in Illinois
• List of unincorporated communities in Illinois
• National Association of Counties
• National Register of Historic Places listings in Illinois

• Hébert, Michael L. (2012). "Illinois County Boundaries: 1790 - Present". ILGenWeb. Archived from the original on January 26, 2016. Retrieved June 16, 2010.
• White, Jesse (March 2010). "Origin and Evolution of Illinois Counties" (PDF). Illinois Secretary of State.

Wikimedia Commons has media related to Counties of Illinois.

• Census 2000 U.S. Gazetteer Files
• Illinois Association of County Board Members
• Illinois Association of County Officials
• Illinois City/County Management Association