List of counties in Illinois

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

See also: List of United States counties and county equivalents

Counties of Illinois
LocationState of Illinois
Number102
Populations4,836 (Hardin) – 5,194,675 (Cook)
Areas160 square miles (410 km2) (Putnam) – 1,184 square miles (3,070 km2) (McLean)
GovernmentCounty government
Subdivisions261 Precincts
1,433 Townships

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 2010 Census.

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 the family 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.

Counties

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[2] Area[2] Map
Adams County 001 Quincy1825Pike CountyJohn Quincy Adams (1767–1848), sixth President of the United States 65,691 855 sq mi
(2,214 km2)
Alexander County 003 Cairo1819Union CountyWilliam M. Alexander, settler and state representative in the Illinois General Assembly 6,060 235 sq mi
(609 km2)
Bond County 005 Greenville1817Crawford County, Edwards County, and Madison CountyShadrach Bond (1773–1832), first Governor of Illinois 16,630 380 sq mi
(984 km2)
Boone County 007 Belvidere1837Winnebago CountyDaniel Boone (1734–1820), trailblazer of the Wilderness Road in Kentucky 53,577 280 sq mi
(725 km2)
Brown County 009 Mount Sterling1839Schuyler CountyJacob Brown (1775–1828), successful War of 1812 army officer responsible for Great Lakes defenses 6,556 305 sq mi
(790 km2)
Bureau County 011 Princeton1837Putnam CountyPierre de Bureo, Frenchman, North American fur trader 32,993 869 sq mi
(2,251 km2)
Calhoun County 013 Hardin1825Pike CountyJohn C. Calhoun (1782–1850), South Carolina senator and seventh Vice President of the United States 4,802 253 sq mi
(655 km2)
Carroll County 015 Mount Carroll1839Jo DaviessCharles Carroll of Carrollton (1737–1832), signed the Declaration of Independence on behalf of Maryland 14,312 445 sq mi
(1,153 km2)
Cass County 017 Virginia1837Morgan CountyLewis Cass (1782–1866), second governor of Michigan Territory, fourteenth United States Secretary of War 12,260 375 sq mi
(971 km2)
Champaign County 019 Urbana1833Vermilion CountyChampaign County, Ohio, which took its name from the French for "open level country" 209,983 996 sq mi
(2,580 km2)
Christian County 021 Taylorville1839Sangamon CountyChristian County, Kentucky, which was itself named after Colonel William Christian 32,661 709 sq mi
(1,836 km2)
Clark County 023 Marshall1819Crawford CountyGeorge Rogers Clark (1752–1818), highest-ranking officer in the Northwest Territory during the American Revolution 15,596 501 sq mi
(1,298 km2)
Clay County 025 Louisville1824Wayne, Lawrence, Fayette, and Crawford CountyHenry Clay (1777–1852), Kentucky legislator who negotiated the Missouri Compromise 13,253 468 sq mi
(1,212 km2)
Clinton County 027 Carlyle1824Washington, Bond, and Fayette CountyDeWitt Clinton (1769–1828), Governor of New York, responsible for the construction of the Erie Canal 37,639 474 sq mi
(1,228 km2)
Coles County 029 Charleston1830Clark and Edgar CountyEdward Coles (1786–1868), second Governor of Illinois, responsible for the abolition of slavery in Illinois 50,885 508 sq mi
(1,316 km2)
Cook County 031 Chicago1831Putnam CountyDaniel Pope Cook (1794–1827), politician and first Attorney General of Illinois 5,180,493 944 sq mi
(2,445 km2)
Crawford County 033 Robinson1816Edwards CountyWilliam H. Crawford (1772–1834), ninth United States Secretary of War, seventh Secretary of the Treasury 18,807 443 sq mi
(1,147 km2)
Cumberland County 035 Toledo1843Coles CountyDisputed: Cumberland Road, which entered the county; Cumberland, Maryland; or Cumberland River in Kentucky 10,808 345 sq mi
(894 km2)
DeKalb County 037 Sycamore1837Kane CountyJohann de Kalb (1721–1780), German soldier in the Continental Army who fought alongside Gilbert du Motier, marquis de Lafayette 104,143 631 sq mi
(1,634 km2)
DeWitt County 039 Clinton1839Macon and McLean CountyDeWitt Clinton (1769–1828), Governor of New York, responsible for the construction of the Erie Canal 15,769 397 sq mi
(1,028 km2)
Douglas County 041 Tuscola1859Coles CountyStephen A. Douglas (1813–1861), prominent Illinois Democrat who engaged in debates with Abraham Lincoln 19,479 416 sq mi
(1,077 km2)
DuPage County 043 Wheaton1839Cook CountyDuPage River 928,589 327 sq mi
(847 km2)
Edgar County 045 Paris1823Clark CountyJohn Edgar (c. 1750–1832), Illinois delegate to the Northwest Territory legislature; at the time, wealthiest man in Illinois 17,360 623 sq mi
(1,614 km2)
Edwards County 047 Albion1814Gallatin County and Madison CountyNinian Edwards (1775–1833), third Governor of the State of Illinois and only governor of the Illinois Territory 6,392 222 sq mi
(575 km2)
Effingham County 049 Effingham1831Fayette and Crawford CountyThomas Howard, 3rd Earl of Effingham, military officer who resigned from the British Army to avoid fighting the American colonies 34,208 478 sq mi
(1,238 km2)
Fayette County 051 Vandalia1821Bond, Wayne, Clark, Jefferson, and Crawford CountyGilbert du Motier, marquis de Lafayette (1757–1834), French military officer who was a key factor in the American and French Revolutions. 21,416 716 sq mi
(1,854 km2)
Ford County 053 Paxton1859Vermilion CountyThomas Ford (1800–1850), eighth Governor of Illinois; served during the Illinois Mormon War 13,264 485 sq mi
(1,256 km2)
Franklin County 055 Benton1818White County and Gallatin CountyBenjamin Franklin (1706–1790), prolific writer, inventor, and politician; key factor in the American Revolution 38,701 408 sq mi
(1,057 km2)
Fulton County 057 Lewistown1823Pike CountyRobert Fulton (1765–1815), inventor of the steamboat 34,844 865 sq mi
(2,240 km2)
Gallatin County 059 Shawneetown1812Randolph CountyAlbert Gallatin (1761–1849), fourth and longest-serving United States Secretary of the Treasury 5,058 322 sq mi
(834 km2)
Greene County 061 Carrollton1821Madison CountyNathanael Greene (1742–1786), major general in the Continental Army 13,044 543 sq mi
(1,406 km2)
Grundy County 063 Morris1841LaSalle CountyFelix Grundy (1777–1840), Tennessean senator who served as the thirteenth United States Attorney General 50,972 418 sq mi
(1,083 km2)
Hamilton County 065 McLeansboro1821White CountyAlexander Hamilton (1755–1804), first United States Secretary of the Treasury 8,163 434 sq mi
(1,124 km2)
Hancock County 067 Carthage1825Adams CountyJohn Hancock (1737–1793), first governor of the Massachusetts colony and president of the Second Continental Congress 17,844 793 sq mi
(2,054 km2)
Hardin County 069 Elizabethtown1839Pope CountyHardin County, Kentucky, which was itself named after John Hardin 3,910 177 sq mi
(458 km2)
Henderson County 071 Oquawka1841Warren CountyHenderson County, Kentucky, which was itself named after Richard Henderson 6,709 378 sq mi
(979 km2)
Henry County 073 Cambridge1825Fulton CountyPatrick Henry (1736–1799), American Revolutionary War figure; first and sixth Governor of Virginia 49,090 822 sq mi
(2,129 km2)
Iroquois County 075 Watseka1833Vermilion CountyIroquois Native Americans 27,604 1,117 sq mi
(2,893 km2)
Jackson County 077 Murphysboro1816Randolph County and Johnson CountyAndrew Jackson (1767–1845), seventh President of the United States, United States Senator from Tennessee, and general in the War of 1812 57,419 584 sq mi
(1,513 km2)
Jasper County 079 Newton1831Clay and Crawford CountySgt. William Jasper (c. 1750–1779), American Revolutionary War soldier popularized by Parson Weems 9,611 494 sq mi
(1,279 km2)
Jefferson County 081 Mount Vernon1819Edwards and White CountyThomas 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 37,820 571 sq mi
(1,479 km2)
Jersey County 083 Jerseyville1839Greene CountyState of New Jersey, from which many early settlers hailed 21,847 369 sq mi
(956 km2)
Jo Daviess County 085 Galena1827Henry, Mercer, and Putnam CountyJoseph Hamilton Daveiss (1774–1811), commander of the Indiana Dragoons at the Battle of Tippecanoe 21,366 600 sq mi
(1,554 km2)
Johnson County 087 Vienna1812Randolph CountyRichard Mentor Johnson (c. 1780–1850), ninth Vice President of the United States and United States Senator from Kentucky 12,456 343 sq mi
(888 km2)
Kane County 089 Geneva1836LaSalle CountyElias Kane (1794–1835), United States Senator from Illinois 534,216 519 sq mi
(1,344 km2)
Kankakee County 091 Kankakee1853Iroquois and Will CountyKankakee River 110,024 676 sq mi
(1,751 km2)
Kendall County 093 Yorkville1841LaSalle and Kane CountyAmos Kendall (1789–1869), United States Postmaster General under Presidents Andrew Jackson and Martin Van Buren 127,915 320 sq mi
(829 km2)
Knox County 095 Galesburg1825Fulton CountyGen. Henry Knox (1750–1806), American Revolutionary War general and first United States Secretary of War 50,112 716 sq mi
(1,854 km2)
Lake County 097 Waukegan1839McHenry CountyLake Michigan 700,832 443 sq mi
(1,147 km2)
LaSalle County 099 Ottawa1831Putnam and Tazewell CountySieur de la Salle (1643–1687), French explorer of the Great Lakes 109,430 1,135 sq mi
(2,940 km2)
Lawrence County 101 Lawrenceville1821Crawford and Edwards CountyCapt. James Lawrence (1781–1813), commander of the USS Chesapeake in the War of 1812. Famous for his command "Don't give up the ship!" 15,765 372 sq mi
(963 km2)
Lee County 103 Dixon1839Ogle County"Light Horse" Henry Lee III (1756–1818), American Revolutionary War officer and ninth Governor of Virginia 34,223 724 sq mi
(1,875 km2)
Livingston County 105 Pontiac1837LaSalle and McLean CountyEdward Livingston (1764–1836), prominent jurist, Congressman from New York and Louisiana, and U.S. Secretary of State from 1831-33 35,761 1,043 sq mi
(2,701 km2)
Logan County 107 Lincoln1839Sangamon CountyJohn Logan, country doctor and early settler, and the father of John A. Logan 28,925 618 sq mi
(1,601 km2)
Macon County 115 Decatur1829Shelby CountyNathaniel Macon (1758–1837), sixth Speaker of the United States House of Representatives and United States Senator from North Carolina 104,712 580 sq mi
(1,502 km2)
Macoupin County 117 Carlinville1829Greene CountyNative American word macoupin, meaning "American lotus" 45,313 862 sq mi
(2,233 km2)
Madison County 119 Edwardsville1812St. Clair County and Randolph CountyJames Madison (1751–1836), fourth President of the United States and principal author of the Constitution of the United States 264,461 716 sq mi
(1,854 km2)
Marion County 121 Salem1823Fayette and Jefferson CountyFrancis Marion (c. 1732–1795), general in the American Revolutionary War known as "The Swamp Fox" 37,620 572 sq mi
(1,481 km2)
Marshall County 123 Lacon1839Putnam CountyJohn 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 11,534 386 sq mi
(1,000 km2)
Mason County 125 Havana1841Tazewell and Menard CountyNamed after Mason County, Kentucky, itself named after George Mason 13,565 539 sq mi
(1,396 km2)
Massac County 127 Metropolis1843Pope and Johnson CountyFort Massac, a colonial-era fort on the Ohio River 14,080 237 sq mi
(614 km2)
McDonough County 109 Macomb1826Schuyler CountyCommodore Thomas Macdonough (1783–1825), commander of American naval forces at the Battle of Plattsburgh 29,955 589 sq mi
(1,526 km2)
McHenry County 111 Woodstock1836Cook and LaSalle CountyMajor William McHenry (c. 1771–1835), officer during several campaigns against Native Americans and was a member of the Illinois legislature 308,570 603 sq mi
(1,562 km2)
McLean County 113 Bloomington1830Tazewell CountyJohn McLean (1791–1830), United States Representative and United States Senator from Illinois (the latter from 1824-25 and 1829-30) 172,828 1,183 sq mi
(3,064 km2)
Menard County 129 Petersburg1839Sangamon CountyPierre Menard (1766–1844), prominent early settler and first Lieutenant Governor of Illinois 12,288 314 sq mi
(813 km2)
Mercer County 131 Aledo1825Schuyler CountyHugh Mercer (1726–1777), British officer in the Seven Years' War and general in the Continental Army during the American Revolutionary War 15,601 561 sq mi
(1,453 km2)
Monroe County 133 Waterloo1816Randolph County and St. Clair CountyJames 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 34,335 385 sq mi
(997 km2)
Montgomery County 135 Hillsboro1821Bond and Madison CountyGen. Richard Montgomery (1738–1775), brigadier-general in the Continental Army who led the unsuccessful invasion of Canada 28,601 703 sq mi
(1,821 km2)
Morgan County 137 Jacksonville1823Sangamon CountyGen. Daniel Morgan (1736–1802), successful tactician in the American Revolutionary War and later United States Representative from Virginia 33,976 568 sq mi
(1,471 km2)
Moultrie County 139 Sullivan1843Shelby and Macon CountyGen. William Moultrie (1730–1805), American Revolutionary War general and Governor of South Carolina 14,717 335 sq mi
(868 km2)
Ogle County 141 Oregon1836Jo DaviessJoseph Ogle (1737–1821), early settler in southwest Illinois, who helped found the first Methodist church in Illinois 50,923 758 sq mi
(1,963 km2)
Peoria County 143 Peoria1825Fulton CountyThe Peoria Native American tribe 180,621 618 sq mi
(1,601 km2)
Perry County 145 Pinckneyville1827Randolph and Jackson CountyCommodore Oliver Hazard Perry (1785–1819), American naval officer who led the victorious American forces at the Battle of Lake Erie 21,174 441 sq mi
(1,142 km2)
Piatt County 147 Monticello1841DeWitt and Macon CountyJames A. Piatt, the patriarch of a prominent settler family in the early history of the county 16,396 439 sq mi
(1,137 km2)
Pike County 149 Pittsfield1821Madison, Bond, and Clark CountyZebulon Pike (1779–1813), early explorer of the American Southwest, namesake of Pikes Peak 15,611 831 sq mi
(2,152 km2)
Pope County 151 Golconda1816Gallatin and Johnson CountyNathaniel Pope (1784–1850), early Delegate from Illinois Territory to Congress and judge on the United States District Court for the District of Illinois 4,212 368 sq mi
(953 km2)
Pulaski County 153 Mound City1843Alexander and Johnson CountyGen. Casimir Pulaski (1745–1779), Polish American general of cavalry in the American Revolutionary War 5,463 199 sq mi
(515 km2)
Putnam County 155 Hennepin1825Fulton CountyGen. Israel Putnam (1718–1790), commander of American forces at the Battle of Bunker Hill 5,740 160 sq mi
(414 km2)
Randolph County 157 Chester1795St. Clair CountyEdmund Randolph (1753–1813), first Attorney General of the United States, and briefly United States Secretary of State 32,106 575 sq mi
(1,489 km2)
Richland County 159 Olney1841Clay and Lawrence CountyRichland County, Ohio, itself named for its rich soil 15,763 360 sq mi
(932 km2)
Rock Island County 161 Rock Island1831Jo Daviess CountyRock Island 143,477 427 sq mi
(1,106 km2)
Saline County 165 Harrisburg1847Gallatin CountySalt springs within the county 23,906 379 sq mi
(982 km2)
Sangamon County 167 Springfield1821Madison and Bond CountySangamon River 195,348 868 sq mi
(2,248 km2)
Schuyler County 169 Rushville1825Pike and Fulton CountyGen. Philip Schuyler (1733–1804), American Revolutionary War general and United States Senator from New York 6,907 437 sq mi
(1,132 km2)
Scott County 171 Winchester1839Morgan CountyScott County, Kentucky, itself named after Charles Scott 4,926 250 sq mi
(647 km2)
Shelby County 173 Shelbyville1827Fayette CountyIsaac Shelby (1750–1826), soldier in the American Revolutionary War and War of 1812; first and fifth Governor of Kentucky 21,741 758 sq mi
(1,963 km2)
St. Clair County 163 Belleville1790original two countiesArthur St. Clair (1737–1818), major general in the American Revolutionary War and first Governor of the Northwest Territory 261,059 657 sq mi
(1,702 km2)
Stark County 175 Toulon1839Knox and Putnam CountyGen. John Stark (1728–1822), general in the American Revolutionary War, called the "Hero of Bennington" 5,427 288 sq mi
(746 km2)
Stephenson County 177 Freeport1837Jo Daviess and Winnebago CountyBenjamin Stephenson (1769–1822), representative of Illinois Territory in the United States Congress from 1814 to 1816 44,753 564 sq mi
(1,461 km2)
Tazewell County 179 Pekin1827Sangamon CountyLittleton Waller Tazewell (1774–1860), United States Senator from (and later governor of) Virginia 132,328 646 sq mi
(1,673 km2)
Union County 181 Jonesboro1818Johnson CountyThe federal union of the states 16,841 413 sq mi
(1,070 km2)
Vermilion County 183 Danville1826Edgar CountyThe Vermilion River 76,806 898 sq mi
(2,326 km2)
Wabash County 185 Mount Carmel1824Edwards CountyThe Wabash River 11,549 223 sq mi
(578 km2)
Warren County 187 Monmouth1825Schuyler CountyJoseph Warren (1741–1775), played a role in American Patriot movements, a prominent early fatality in the American Revolutionary War 17,032 542 sq mi
(1,404 km2)
Washington County 189 Nashville1818St. Clair CountyGeorge Washington (1732–1799), commander-in-chief of American forces in the American Revolutionary War and first President of the United States 13,995 562 sq mi
(1,456 km2)
Wayne County 191 Fairfield1819Edwards CountyGen. "Mad" Anthony Wayne (1745–1796), major general in the United States Army in the American Revolutionary War and the Northwest Indian War 16,332 713 sq mi
(1,847 km2)
White County 193 Carmi1815Gallatin CountyIsaac White (1776–1811), resident of Illinois who enlisted in the Indiana militia and was killed at the Battle of Tippecanoe 13,665 494 sq mi
(1,279 km2)
Whiteside County 195 Morrison1836Jo Daviess and Henry CountySamuel Whiteside (1783–1868), state legislator and militia leader 55,626 684 sq mi
(1,772 km2)
Will County 197 Joliet1836Cook and Iroquois CountyConrad Will (1779–1835),[5] physician, local businessman and longtime member of the state legislature 692,310 835 sq mi
(2,163 km2)
Williamson County 199 Marion1839Franklin CountyHugh Williamson (1735–1819), delegate from North Carolina to the Philadelphia Convention 67,056 420 sq mi
(1,088 km2)
Winnebago County 201 Rockford1836Jo DaviessWinnebago Native Americans 284,081 513 sq mi
(1,329 km2)
Woodford County 203 Eureka1841Tazewell and McLean CountyGen. William Woodford (1734–1780), brigadier general in the American Revolutionary War who died while a British prisoner 38,463 527 sq mi
(1,365 km2)

Defunct counties

See also

Notes
  1. "U.S. Census Bureau 2019 FIPS Codes". census.gov. Retrieved January 8, 2021.
  2. "County Explorer". National Association of Counties. Retrieved January 8, 2021.
  3. "Illinois County Biographies". Genealogy Trails.com. Genealogy Trails. 2000. Retrieved September 21, 2008.
  4. "The Origin of Illinois County Names". Genealogy Trails.com. Genealogy Trails. 2000. Retrieved September 21, 2008.
  5. Matile, Roger (June 22, 2006). "Reflections: Was Dr. Conrad Will really worth his salt?". Ledger-Sentinel. Retrieved October 11, 2011.

References
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