There are 102 counties in the state of Illinois.

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.

Even though Illinois does not have a Lincoln County named after its favorite son, Abraham Lincoln, it does have a Douglas County named after his political rival Stephen A. Douglas. It also has Calhoun County, named after John C. Calhoun, outspoken for his southern views in the years preceding the American Civil War. Many 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 Northern heroes of the Civil War, mainly because the counties were almost all named before that war. The state even has a Lee County named after the family of Robert E. Lee, who at one time served in Illinois. Illinois also has a singular distinction of having two counties named after the same person, DeWitt Clinton.

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.

Illinois's postal abbreviation is IL and its FIPS state code is 17.


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

FIPS code
County seat

Adams County 001 Quincy 1825 Pike County John Quincy Adams (1767–1848), sixth President of the United States &&&&&&&&&&067103.&&&&&067,103 &&&&&&&&&&&&0857.&&&&&0857 sq mi
(&&&&&&&&&&&02220.&&&&&02,220 km2)
State map highlighting Adams County
Alexander County 003 Cairo 1819 Union County William M. Alexander, a settler and state representative in the Illinois General Assembly &&&&&&&&&&&08238.&&&&&08,238 &&&&&&&&&&&&0236.&&&&&0236 sq mi
(&&&&&&&&&&&&0611.&&&&&0611 km2)
State map highlighting Alexander County
Bond County 005 Greenville 1817 Crawford County, Edwards County, and Madison County Shadrach Bond (1773–1832), First Governor of Illinois &&&&&&&&&&017768.&&&&&017,768 &&&&&&&&&&&&0380.&&&&&0380 sq mi
(&&&&&&&&&&&&0984.&&&&&0984 km2)
State map highlighting Bond County
Boone County 007 Belvidere 1837 Winnebago County Daniel Boone (1734-1820), trailblazer of the Wilderness Road in Kentucky &&&&&&&&&&054165.&&&&&054,165 &&&&&&&&&&&&0281.&&&&&0281 sq mi
(&&&&&&&&&&&&0728.&&&&&0728 km2)
State map highlighting Boone County
Brown County 009 Mount Sterling 1839 Schuyler County Jacob Brown (1775–1828), a successful American Revolution army officer responsible for Great Lakes defenses &&&&&&&&&&&06937.&&&&&06,937 &&&&&&&&&&&&0306.&&&&&0306 sq mi
(&&&&&&&&&&&&0793.&&&&&0793 km2)
State map highlighting Brown County
Bureau County 011 Princeton 1837 Putnam County Pierre de Bureo, Frenchman, North American fur trader &&&&&&&&&&034978.&&&&&034,978 &&&&&&&&&&&&0869.&&&&&0869 sq mi
(&&&&&&&&&&&02251.&&&&&02,251 km2)
State map highlighting Bureau County
Calhoun County 013 Hardin 1825 Pike County John C. Calhoun (1782–1850), South Carolina senator and seventh Vice President of the United States &&&&&&&&&&&05089.&&&&&05,089 &&&&&&&&&&&&0254.&&&&&0254 sq mi
(&&&&&&&&&&&&0658.&&&&&0658 km2)
State map highlighting Calhoun County
Carroll County 015 Mount Carroll 1839 Jo Daviess Charles Carroll of Carrollton (1737–1832), signed the Declaration of Independence on behalf of Maryland &&&&&&&&&&015387.&&&&&015,387 &&&&&&&&&&&&0444.&&&&&0444 sq mi
(&&&&&&&&&&&01150.&&&&&01,150 km2)
State map highlighting Carroll County
Cass County 017 Virginia 1837 Morgan County Lewis Cass (1782–1866), second governor of Michigan Territory, fourteenth United States Secretary of War &&&&&&&&&&013642.&&&&&013,642 &&&&&&&&&&&&0376.&&&&&0376 sq mi
(&&&&&&&&&&&&0974.&&&&&0974 km2)
State map highlighting Cass County
Champaign County 019 Urbana 1833 Vermilion County Champaign County, Ohio, which took its name from the French for "open level country" &&&&&&&&&0201081.&&&&&0201,081 &&&&&&&&&&&&0997.&&&&&0997 sq mi
(&&&&&&&&&&&02582.&&&&&02,582 km2)
State map highlighting Champaign County
Christian County 021 Taylorville 1839 Sangamon County Christian County, Kentucky, which was itself named after Colonel William Christian &&&&&&&&&&034800.&&&&&034,800 &&&&&&&&&&&&0709.&&&&&0709 sq mi
(&&&&&&&&&&&01836.&&&&&01,836 km2)
State map highlighting Christian County
Clark County 023 Marshall 1819 Crawford County George Rogers Clark (1752–1818), highest-ranking officer in the Northwest Territory during the American Revolution &&&&&&&&&&016335.&&&&&016,335 &&&&&&&&&&&&0502.&&&&&0502 sq mi
(&&&&&&&&&&&01300.&&&&&01,300 km2)
State map highlighting Clark County
Clay County 025 Louisville 1824 Wayne, Lawrence, Fayette, and Crawford County Henry Clay (1777–1852), Kentucky legislator who negotiated the Missouri Compromise &&&&&&&&&&013815.&&&&&013,815 &&&&&&&&&&&&0469.&&&&&0469 sq mi
(&&&&&&&&&&&01215.&&&&&01,215 km2)
State map highlighting Clay County
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 &&&&&&&&&&037762.&&&&&037,762 &&&&&&&&&&&&0474.&&&&&0474 sq mi
(&&&&&&&&&&&01228.&&&&&01,228 km2)
State map highlighting Clinton County
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 &&&&&&&&&&053873.&&&&&053,873 &&&&&&&&&&&&0508.&&&&&0508 sq mi
(&&&&&&&&&&&01316.&&&&&01,316 km2)
State map highlighting Coles County
Cook County 031 Chicago 1831 Putnam County Daniel Pope Cook (1794–1827), politician and first Attorney General of Illinois &&&&&&&&05194675.&&&&&05,194,675 &&&&&&&&&&&&0946.&&&&&0946 sq mi
(&&&&&&&&&&&02450.&&&&&02,450 km2)
State map highlighting Cook County
Crawford County 033 Robinson 1816 Edwards County William H. Crawford (1772–1834), ninth United States Secretary of War, seventh Secretary of the Treasury &&&&&&&&&&019817.&&&&&019,817 &&&&&&&&&&&&0444.&&&&&0444 sq mi
(&&&&&&&&&&&01150.&&&&&01,150 km2)
State map highlighting Crawford County
Cumberland County 035 Toledo 1843 Coles County Disputed: Cumberland Road, which entered the county; Cumberland, Maryland; or Cumberland River in Kentucky &&&&&&&&&&011048.&&&&&011,048 &&&&&&&&&&&&0346.&&&&&0346 sq mi
(&&&&&&&&&&&&0896.&&&&&0896 km2)
State map highlighting Cumberland County
DeKalb County 037 Sycamore 1837 Kane County Johann de Kalb (1721–80), German soldier in the Continental Army who fought alongside Gilbert du Motier, marquis de Lafayette &&&&&&&&&0105160.&&&&&0105,160 &&&&&&&&&&&&0634.&&&&&0634 sq mi
(&&&&&&&&&&&01642.&&&&&01,642 km2)
State map highlighting DeKalb County
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 &&&&&&&&&&016561.&&&&&016,561 &&&&&&&&&&&&0398.&&&&&0398 sq mi
(&&&&&&&&&&&01031.&&&&&01,031 km2)
State map highlighting DeWitt County
Douglas County 041 Tuscola 1859 Coles County Stephen A. Douglas (1813–61), prominent Illinois Democrat who engaged in debates with Abraham Lincoln &&&&&&&&&&019980.&&&&&019,980 &&&&&&&&&&&&0417.&&&&&0417 sq mi
(&&&&&&&&&&&01080.&&&&&01,080 km2)
State map highlighting Douglas County
DuPage County 043 Wheaton 1839 Cook County DuPage River &&&&&&&&&0916924.&&&&&0916,924 &&&&&&&&&&&&0334.&&&&&0334 sq mi
(&&&&&&&&&&&&0865.&&&&&0865 km2)
State map highlighting DuPage County
Edgar County 045 Paris 1823 Clark County John Edgar (c. 1750–1832), Illinois delegate to the Northwest Territory legislature; at time, wealthiest man in Illinois &&&&&&&&&&018576.&&&&&018,576 &&&&&&&&&&&&0624.&&&&&0624 sq mi
(&&&&&&&&&&&01616.&&&&&01,616 km2)
State map highlighting Edgar County
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 &&&&&&&&&&&06721.&&&&&06,721 &&&&&&&&&&&&0222.&&&&&0222 sq mi
(&&&&&&&&&&&&0575.&&&&&0575 km2)
State map highlighting Edwards County
Effingham County 049 Effingham 1831 Fayette and Crawford County Lord Edward Effingham, military officer who resigned from the British Army to avoid fighting the American colonies &&&&&&&&&&034242.&&&&&034,242 &&&&&&&&&&&&0479.&&&&&0479 sq mi
(&&&&&&&&&&&01241.&&&&&01,241 km2)
State map highlighting Effingham County
Fayette County 051 Vandalia 1821 Bond, Wayne, Clark, Jefferson, and Crawford County Marquis de la Fayette (1757–1834), French military officer who was a key factor in the American and French Revolutions. &&&&&&&&&&022140.&&&&&022,140 &&&&&&&&&&&&0716.&&&&&0716 sq mi
(&&&&&&&&&&&01854.&&&&&01,854 km2)
State map highlighting Fayette County
Ford County 053 Paxton 1859 Vermilion County Thomas Ford (1800–50), eighth Governor of Illinois; served during the Illinois Mormon War &&&&&&&&&&014081.&&&&&014,081 &&&&&&&&&&&&0486.&&&&&0486 sq mi
(&&&&&&&&&&&01259.&&&&&01,259 km2)
State map highlighting Ford County
Franklin County 055 Benton 1818 White County and Gallatin County Benjamin Franklin (1706–90), prolific writer, inventor, and politician; key factor in the American Revolution &&&&&&&&&&039561.&&&&&039,561 &&&&&&&&&&&&0412.&&&&&0412 sq mi
(&&&&&&&&&&&01067.&&&&&01,067 km2)
State map highlighting Franklin County
Fulton County 057 Lewistown 1823 Pike County Robert Fulton (1765–1815), inventor of the steamboat &&&&&&&&&&037069.&&&&&037,069 &&&&&&&&&&&&0866.&&&&&0866 sq mi
(&&&&&&&&&&&02243.&&&&&02,243 km2)
State map highlighting Fulton County
Gallatin County 059 Shawneetown 1812 Randolph County Albert Gallatin (1761–1849), fourth and longest-serving United States Secretary of the Treasury &&&&&&&&&&&05589.&&&&&05,589 &&&&&&&&&&&&0324.&&&&&0324 sq mi
(&&&&&&&&&&&&0839.&&&&&0839 km2)
State map highlighting Gallatin County
Greene County 061 Carrollton 1821 Madison County Nathanael Greene (1742–86), major general in the Continental Army &&&&&&&&&&013886.&&&&&013,886 &&&&&&&&&&&&0543.&&&&&0543 sq mi
(&&&&&&&&&&&01406.&&&&&01,406 km2)
State map highlighting Greene County
Grundy County 063 Morris 1841 LaSalle County Felix Grundy (1777–1840), Tennessean senator that served as the thirteenth United States Attorney General &&&&&&&&&&050063.&&&&&050,063 &&&&&&&&&&&&0420.&&&&&0420 sq mi
(&&&&&&&&&&&01088.&&&&&01,088 km2)
State map highlighting Grundy County
Hamilton County 065 McLeansboro 1821 White County Alexander Hamilton (1755–1804), first United States Secretary of the Treasury &&&&&&&&&&&08457.&&&&&08,457 &&&&&&&&&&&&0435.&&&&&0435 sq mi
(&&&&&&&&&&&01127.&&&&&01,127 km2)
State map highlighting Hamilton County
Hancock County 067 Carthage 1825 Adams County John Hancock (1737–93), first governor of the Massachusetts colony and president of the Second Continental Congress &&&&&&&&&&019104.&&&&&019,104 &&&&&&&&&&&&0795.&&&&&0795 sq mi
(&&&&&&&&&&&02059.&&&&&02,059 km2)
State map highlighting Hancock County
Hardin County 069 Elizabethtown 1839 Pope County Hardin County, Kentucky, which was itself named after John Hardin &&&&&&&&&&&04320.&&&&&04,320 &&&&&&&&&&&&0178.&&&&&0178 sq mi
(&&&&&&&&&&&&0461.&&&&&0461 km2)
State map highlighting Hardin County
Henderson County 071 Oquawka 1841 Warren County Henderson County, Kentucky, which was itself named after Richard Henderson &&&&&&&&&&&07331.&&&&&07,331 &&&&&&&&&&&&0379.&&&&&0379 sq mi
(&&&&&&&&&&&&0982.&&&&&0982 km2)
State map highlighting Henderson County
Henry County 073 Cambridge 1825 Fulton County Patrick Henry (1736-99), American Revolutionary War figure and first and sixth Governor of Virginia &&&&&&&&&&050486.&&&&&050,486 &&&&&&&&&&&&0823.&&&&&0823 sq mi
(&&&&&&&&&&&02132.&&&&&02,132 km2)
State map highlighting Henry County
Iroquois County 075 Watseka 1833 Vermilion County Iroquois Native Americans &&&&&&&&&&029718.&&&&&029,718 &&&&&&&&&&&01116.&&&&&01,116 sq mi
(&&&&&&&&&&&02890.&&&&&02,890 km2)
State map highlighting Iroquois County
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 &&&&&&&&&&060218.&&&&&060,218 &&&&&&&&&&&&0588.&&&&&0588 sq mi
(&&&&&&&&&&&01523.&&&&&01,523 km2)
State map highlighting Jackson County
Jasper County 079 Newton 1831 Clay and Crawford County Sgt. William Jasper (c. 1750-79), American Revolutionary War soldier popularized by Parson Weems &&&&&&&&&&&09698.&&&&&09,698 &&&&&&&&&&&&0494.&&&&&0494 sq mi
(&&&&&&&&&&&01279.&&&&&01,279 km2)
State map highlighting Jasper County
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 &&&&&&&&&&038827.&&&&&038,827 &&&&&&&&&&&&0571.&&&&&0571 sq mi
(&&&&&&&&&&&01479.&&&&&01,479 km2)
State map highlighting Jefferson County
Jersey County 083 Jerseyville 1839 Greene County State of New Jersey, from which many early settlers hailed &&&&&&&&&&022985.&&&&&022,985 &&&&&&&&&&&&0369.&&&&&0369 sq mi
(&&&&&&&&&&&&0956.&&&&&0956 km2)
State map highlighting Jersey County
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 &&&&&&&&&&022678.&&&&&022,678 &&&&&&&&&&&&0601.&&&&&0601 sq mi
(&&&&&&&&&&&01557.&&&&&01,557 km2)
State map highlighting Jo Daviess County
Johnson County 087 Vienna 1812 Randolph County Richard Mentor Johnson (abt. 1780-1850), ninth Vice President of the United States and United States Senator form Kentucky &&&&&&&&&&012582.&&&&&012,582 &&&&&&&&&&&&0346.&&&&&0346 sq mi
(&&&&&&&&&&&&0896.&&&&&0896 km2)
State map highlighting Johnson County
Kane County 089 Geneva 1836 LaSalle County Elias Kane (1794-1835), United States Senator from Illinois &&&&&&&&&0515269.&&&&&0515,269 &&&&&&&&&&&&0521.&&&&&0521 sq mi
(&&&&&&&&&&&01349.&&&&&01,349 km2)
State map highlighting Kane County
Kankakee County 091 Kankakee 1853 Iroquois and Will County Kankakee River &&&&&&&&&0113449.&&&&&0113,449 &&&&&&&&&&&&0678.&&&&&0678 sq mi
(&&&&&&&&&&&01756.&&&&&01,756 km2)
State map highlighting Kankakee County
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 &&&&&&&&&0114736.&&&&&0114,736 &&&&&&&&&&&&0321.&&&&&0321 sq mi
(&&&&&&&&&&&&0831.&&&&&0831 km2)
State map highlighting Kendall County
Knox County 095 Galesburg 1825 Fulton County Gen. Henry Knox (1750-1806), American Revolutionary War general and first United States Secretary of War &&&&&&&&&&052919.&&&&&052,919 &&&&&&&&&&&&0716.&&&&&0716 sq mi
(&&&&&&&&&&&01854.&&&&&01,854 km2)
State map highlighting Knox County
Lake County 097 Waukegan 1839 McHenry County Lake Michigan &&&&&&&&&0703462.&&&&&0703,462 &&&&&&&&&&&&0448.&&&&&0448 sq mi
(&&&&&&&&&&&01160.&&&&&01,160 km2)
State map highlighting Lake County
LaSalle County 099 Ottawa 1831 Putnam and Tazewell County Sieur de la Salle (1643-87), French explorer of the Great Lakes. &&&&&&&&&0113924.&&&&&0113,924 &&&&&&&&&&&01135.&&&&&01,135 sq mi
(&&&&&&&&&&&02940.&&&&&02,940 km2)
State map highlighting LaSalle County
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!" &&&&&&&&&&016833.&&&&&016,833 &&&&&&&&&&&&0372.&&&&&0372 sq mi
(&&&&&&&&&&&&0963.&&&&&0963 km2)
State map highlighting Lawrence County
Lee County 103 Dixon 1839 Ogle County "Light Horse" Henry Lee III (1756-1818), American Revolutionary War officer and ninth Governor of Virginia &&&&&&&&&&036031.&&&&&036,031 &&&&&&&&&&&&0725.&&&&&0725 sq mi
(&&&&&&&&&&&01878.&&&&&01,878 km2)
State map highlighting Lee County
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. &&&&&&&&&&038950.&&&&&038,950 &&&&&&&&&&&01044.&&&&&01,044 sq mi
(&&&&&&&&&&&02704.&&&&&02,704 km2)
State map highlighting Livingston County
Logan County 107 Lincoln 1839 Sangamon County John Logan, a country doctor and early settler, and the father of John A. Logan. &&&&&&&&&&030305.&&&&&030,305 &&&&&&&&&&&&0618.&&&&&0618 sq mi
(&&&&&&&&&&&01601.&&&&&01,601 km2)
State map highlighting Logan County
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. &&&&&&&&&0110768.&&&&&0110,768 &&&&&&&&&&&&0581.&&&&&0581 sq mi
(&&&&&&&&&&&01505.&&&&&01,505 km2)
State map highlighting Macon County
Macoupin County 117 Carlinville 1829 Greene County Native American word Macoupin, meaning American lotus &&&&&&&&&&047765.&&&&&047,765 &&&&&&&&&&&&0864.&&&&&0864 sq mi
(&&&&&&&&&&&02238.&&&&&02,238 km2)
State map highlighting Macoupin County
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. &&&&&&&&&0269282.&&&&&0269,282 &&&&&&&&&&&&0725.&&&&&0725 sq mi
(&&&&&&&&&&&01878.&&&&&01,878 km2)
State map highlighting Madison County
Marion County 121 Salem 1823 Fayette and Jefferson County Francis Marion (c. 1732-95), general in the American Revolutionary War known as "The Swamp Fox" &&&&&&&&&&039437.&&&&&039,437 &&&&&&&&&&&&0572.&&&&&0572 sq mi
(&&&&&&&&&&&01481.&&&&&01,481 km2)
State map highlighting Marion County
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 &&&&&&&&&&012640.&&&&&012,640 &&&&&&&&&&&&0386.&&&&&0386 sq mi
(&&&&&&&&&&&01000.&&&&&01,000 km2)
State map highlighting Marshall County
Mason County 125 Havana 1841 Tazewell and Menard County Named after Mason County, Kentucky, itself named after George Mason &&&&&&&&&&014666.&&&&&014,666 &&&&&&&&&&&&0539.&&&&&0539 sq mi
(&&&&&&&&&&&01396.&&&&&01,396 km2)
State map highlighting Mason County
Massac County 127 Metropolis 1843 Pope and Johnson County Fort Massac, a colonial-era fort on the Ohio River &&&&&&&&&&015429.&&&&&015,429 &&&&&&&&&&&&0239.&&&&&0239 sq mi
(&&&&&&&&&&&&0619.&&&&&0619 km2)
State map highlighting Massac County
McDonough County 109 Macomb 1826 Schuyler County Commodore Thomas Macdonough (1783-1825), commander of American naval forces at the Battle of Plattsburgh &&&&&&&&&&032612.&&&&&032,612 &&&&&&&&&&&&0589.&&&&&0589 sq mi
(&&&&&&&&&&&01526.&&&&&01,526 km2)
State map highlighting McDonough County
McHenry County 111 Woodstock 1836 Cook and LaSalle County Major William McHenry (c. 1771-1835), officer in during several campaigns against Native Americans and member of the Illinois legislature &&&&&&&&&0308760.&&&&&0308,760 &&&&&&&&&&&&0604.&&&&&0604 sq mi
(&&&&&&&&&&&01564.&&&&&01,564 km2)
State map highlighting McHenry County
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) &&&&&&&&&0169572.&&&&&0169,572 &&&&&&&&&&&01184.&&&&&01,184 sq mi
(&&&&&&&&&&&03067.&&&&&03,067 km2)
State map highlighting McLean County
Menard County 129 Petersburg 1839 Sangamon County Pierre Menard (1766-1844), prominent early settler and first Lieutenant Governor of Illinois &&&&&&&&&&012705.&&&&&012,705 &&&&&&&&&&&&0314.&&&&&0314 sq mi
(&&&&&&&&&&&&0813.&&&&&0813 km2)
State map highlighting Menard County
Mercer County 131 Aledo 1825 Schuyler County Hugh Mercer (1726-77), British officer in the Seven Years' War and general in the Continental Army during the American Revolutionary War &&&&&&&&&&016434.&&&&&016,434 &&&&&&&&&&&&0561.&&&&&0561 sq mi
(&&&&&&&&&&&01453.&&&&&01,453 km2)
State map highlighting Mercer County
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 &&&&&&&&&&032957.&&&&&032,957 &&&&&&&&&&&&0388.&&&&&0388 sq mi
(&&&&&&&&&&&01005.&&&&&01,005 km2)
State map highlighting Monroe County
Montgomery County 135 Hillsboro 1821 Bond and Madison County Gen. Richard Montgomery (1738-75), brigadier-general in the Continental Army who led the unsuccessful invasion of Canada &&&&&&&&&&030104.&&&&&030,104 &&&&&&&&&&&&0704.&&&&&0704 sq mi
(&&&&&&&&&&&01823.&&&&&01,823 km2)
State map highlighting Montgomery County
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 &&&&&&&&&&035547.&&&&&035,547 &&&&&&&&&&&&0569.&&&&&0569 sq mi
(&&&&&&&&&&&01474.&&&&&01,474 km2)
State map highlighting Morgan County
Moultrie County 139 Sullivan 1843 Shelby and Macon County Gen. William Moultrie (1730-1805), American Revolutionary War general and Governor of South Carolina &&&&&&&&&&014846.&&&&&014,846 &&&&&&&&&&&&0336.&&&&&0336 sq mi
(&&&&&&&&&&&&0870.&&&&&0870 km2)
State map highlighting Moultrie County
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 &&&&&&&&&&053497.&&&&&053,497 &&&&&&&&&&&&0759.&&&&&0759 sq mi
(&&&&&&&&&&&01966.&&&&&01,966 km2)
State map highlighting Ogle County
Peoria County 143 Peoria 1825 Fulton County The Peoria Native American tribe &&&&&&&&&0186494.&&&&&0186,494 &&&&&&&&&&&&0620.&&&&&0620 sq mi
(&&&&&&&&&&&01606.&&&&&01,606 km2)
State map highlighting Peoria County
Perry County 145 Pinckneyville 1827 Randolph and Jackson County Commodore Oliver Hazard Perry (1785-1819), American naval officer who led the victorious American forces at the Battle of Lake Erie &&&&&&&&&&022350.&&&&&022,350 &&&&&&&&&&&&0441.&&&&&0441 sq mi
(&&&&&&&&&&&01142.&&&&&01,142 km2)
State map highlighting Perry County
Piatt County 147 Monticello 1841 DeWitt and Macon County John Piatt, the patriarch of a prominent settler family in the early history of the county &&&&&&&&&&016729.&&&&&016,729 &&&&&&&&&&&&0440.&&&&&0440 sq mi
(&&&&&&&&&&&01140.&&&&&01,140 km2)
State map highlighting Piatt County
Pike County 149 Pittsfield 1821 Madison, Bond, and Clark County Zebulon Pike (1779-1813), early explorer of the American Southwest, namesake of Pikes Peak &&&&&&&&&&016430.&&&&&016,430 &&&&&&&&&&&&0830.&&&&&0830 sq mi
(&&&&&&&&&&&02150.&&&&&02,150 km2)
State map highlighting Pike County
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 &&&&&&&&&&&04470.&&&&&04,470 &&&&&&&&&&&&0371.&&&&&0371 sq mi
(&&&&&&&&&&&&0961.&&&&&0961 km2)
State map highlighting Pope County
Pulaski County 153 Mound City 1843 Alexander and Johnson County Gen. Casimir Pulaski (1745-79), Polish American general of cavalry in the American Revolutionary War &&&&&&&&&&&06161.&&&&&06,161 &&&&&&&&&&&&0201.&&&&&0201 sq mi
(&&&&&&&&&&&&0521.&&&&&0521 km2)
State map highlighting Pulaski County
Putnam County 155 Hennepin 1825 Fulton County Gen. Israel Putnam (1718-90), commander of American forces at the Battle of Bunker Hill &&&&&&&&&&&06006.&&&&&06,006 &&&&&&&&&&&&0160.&&&&&0160 sq mi
(&&&&&&&&&&&&0414.&&&&&0414 km2)
State map highlighting Putnam County
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 &&&&&&&&&&033476.&&&&&033,476 &&&&&&&&&&&&0578.&&&&&0578 sq mi
(&&&&&&&&&&&01497.&&&&&01,497 km2)
State map highlighting Randolph County
Richland County 159 Olney 1841 Clay and Lawrence County Richland County, Ohio, itself named for its rich soil &&&&&&&&&&016233.&&&&&016,233 &&&&&&&&&&&&0360.&&&&&0360 sq mi
(&&&&&&&&&&&&0932.&&&&&0932 km2)
State map highlighting Richland County
Rock Island County 161 Rock Island 1831 Jo Daviess County Rock Island &&&&&&&&&0147546.&&&&&0147,546 &&&&&&&&&&&&0427.&&&&&0427 sq mi
(&&&&&&&&&&&01106.&&&&&01,106 km2)
State map highlighting Rock Island County
Saline County 165 Harrisburg 1847 Gallatin County Salt springs within the county &&&&&&&&&&024913.&&&&&024,913 &&&&&&&&&&&&0383.&&&&&0383 sq mi
(&&&&&&&&&&&&0992.&&&&&0992 km2)
State map highlighting Saline County
Sangamon County 167 Springfield 1821 Madison and Bond County Sangamon River &&&&&&&&&0197465.&&&&&0197,465 &&&&&&&&&&&&0868.&&&&&0868 sq mi
(&&&&&&&&&&&02248.&&&&&02,248 km2)
State map highlighting Sangamon County
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 &&&&&&&&&&&07544.&&&&&07,544 &&&&&&&&&&&&0437.&&&&&0437 sq mi
(&&&&&&&&&&&01132.&&&&&01,132 km2)
State map highlighting Schuyler County
Scott County 171 Winchester 1839 Morgan County Scott County, Kentucky, itself named after Charles Scott &&&&&&&&&&&05355.&&&&&05,355 &&&&&&&&&&&&0251.&&&&&0251 sq mi
(&&&&&&&&&&&&0650.&&&&&0650 km2)
State map highlighting Scott County
Shelby County 173 Shelbyville 1827 Fayette County Isaac Shelby (1750-1826), soldier in the American Revolutionary War and War of 1812, and first and fifth Governor of Kentucky &&&&&&&&&&022363.&&&&&022,363 &&&&&&&&&&&&0759.&&&&&0759 sq mi
(&&&&&&&&&&&01966.&&&&&01,966 km2)
State map highlighting Shelby County
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 &&&&&&&&&0270056.&&&&&0270,056 &&&&&&&&&&&&0664.&&&&&0664 sq mi
(&&&&&&&&&&&01720.&&&&&01,720 km2)
State map highlighting St. Clair County
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" &&&&&&&&&&&05994.&&&&&05,994 &&&&&&&&&&&&0288.&&&&&0288 sq mi
(&&&&&&&&&&&&0746.&&&&&0746 km2)
State map highlighting Stark County
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 &&&&&&&&&&047711.&&&&&047,711 &&&&&&&&&&&&0564.&&&&&0564 sq mi
(&&&&&&&&&&&01461.&&&&&01,461 km2)
State map highlighting Stephenson County
Tazewell County 179 Pekin 1827 Sangamon County Littleton Waller Tazewell (1774-1860), United States Senator from (and later governor of) Virginia &&&&&&&&&0135394.&&&&&0135,394 &&&&&&&&&&&&0649.&&&&&0649 sq mi
(&&&&&&&&&&&01681.&&&&&01,681 km2)
State map highlighting Tazewell County
Union County 181 Jonesboro 1818 Johnson County The federal union of the states &&&&&&&&&&017808.&&&&&017,808 &&&&&&&&&&&&0416.&&&&&0416 sq mi
(&&&&&&&&&&&01077.&&&&&01,077 km2)
State map highlighting Union County
Vermilion County 183 Danville 1826 Edgar County The Vermilion River &&&&&&&&&&081625.&&&&&081,625 &&&&&&&&&&&&0899.&&&&&0899 sq mi
(&&&&&&&&&&&02328.&&&&&02,328 km2)
State map highlighting Vermilion County
Wabash County 185 Mount Carmel 1824 Edwards County The Wabash River &&&&&&&&&&011947.&&&&&011,947 &&&&&&&&&&&&0224.&&&&&0224 sq mi
(&&&&&&&&&&&&0580.&&&&&0580 km2)
State map highlighting Wabash County
Warren County 187 Monmouth 1825 Schuyler County Joseph Warren (1741-75), played a role in American Patriot movements, a prominent early fatality in the American Revolutionary War &&&&&&&&&&017707.&&&&&017,707 &&&&&&&&&&&&0543.&&&&&0543 sq mi
(&&&&&&&&&&&01406.&&&&&01,406 km2)
State map highlighting Warren County
Washington County 189 Nashville 1818 St. Clair County George Washington (1732-99), commander-in-chief of American forces in the American Revolutionary War and first President of the United States &&&&&&&&&&014716.&&&&&014,716 &&&&&&&&&&&&0563.&&&&&0563 sq mi
(&&&&&&&&&&&01458.&&&&&01,458 km2)
State map highlighting Washington County
Wayne County 191 Fairfield 1819 Edwards County Gen. "Mad" Anthony Wayne (1745-96), major general in the United States Army in the American Revolutionary War and the Northwest Indian War &&&&&&&&&&016760.&&&&&016,760 &&&&&&&&&&&&0714.&&&&&0714 sq mi
(&&&&&&&&&&&01849.&&&&&01,849 km2)
State map highlighting Wayne County
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 &&&&&&&&&&014665.&&&&&014,665 &&&&&&&&&&&&0495.&&&&&0495 sq mi
(&&&&&&&&&&&01282.&&&&&01,282 km2)
State map highlighting White County
Whiteside County 195 Morrison 1836 Jo Daviess and Henry County Samuel Whiteside (1783-1868), state legislator and militia leader &&&&&&&&&&058498.&&&&&058,498 &&&&&&&&&&&&0685.&&&&&0685 sq mi
(&&&&&&&&&&&01774.&&&&&01,774 km2)
State map highlighting Whiteside County
Will County 197 Joliet 1836 Cook and Iroquois County Conrad Will (1779-1835),[5] physician, local businessman and longtime member of the state legislature &&&&&&&&&0677560.&&&&&0677,560 &&&&&&&&&&&&0837.&&&&&0837 sq mi
(&&&&&&&&&&&02168.&&&&&02,168 km2)
State map highlighting Will County
Williamson County 199 Marion 1839 Franklin County Hugh Williamson (1735-1819), delegate from North Carolina to the Philadelphia Convention &&&&&&&&&&066357.&&&&&066,357 &&&&&&&&&&&&0424.&&&&&0424 sq mi
(&&&&&&&&&&&01098.&&&&&01,098 km2)
State map highlighting Williamson County
Winnebago County 201 Rockford 1836 Jo Daviess Winnebago Native Americans &&&&&&&&&0295266.&&&&&0295,266 &&&&&&&&&&&&0514.&&&&&0514 sq mi
(&&&&&&&&&&&01331.&&&&&01,331 km2)
State map highlighting Winnebago County
Woodford County 203 Eureka 1841 Tazewell and McLean County Gen. William Woodford (1734-80), brigadier general in the American Revolutionary War who died while a British prisoner &&&&&&&&&&038664.&&&&&038,664 &&&&&&&&&&&&0528.&&&&&0528 sq mi
(&&&&&&&&&&&01368.&&&&&01,368 km2)
State map highlighting Woodford County

Defunct counties

  • 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.

See also

  • 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


  1. ^ "EPA County FIPS Code Listing". Retrieved 2008-02-23. 
  2. ^ a b c d "Find a county". National Association of Counties. Retrieved 2012-09-26. 
  3. ^ "Illinois County Biographies". Genealogy Genealogy Trails. 2000. Retrieved 2008-09-21. 
  4. ^ "The Origin of Illinois County Names". Genealogy Genealogy Trails. 2000. Retrieved 2008-09-21. 
  5. ^ Matile, Roger (22 June 2006). "Reflections: Was Dr. Conrad Will really worth his salt?". Ledger-Sentinel. Retrieved 11 October 2011. 


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This page uses content from the English language Wikipedia. The original content was at List of counties in Illinois. The list of authors can be seen in the page history. As with this Familypedia wiki, the content of Wikipedia is available under the Creative Commons License.