County
FIPS code
County seat
Established
Origin
Etymology
Population
Area
Map
|
Adams County
001
Quincy
1825
Pike County
John Quincy Adams(1767–1848), sixthPresident of the United States
67,103
857sqmi
(2,220km)
|
Alexander County
003
Cairo
1819
Union County
William M. Alexander, a settler and state representative in theIllinois General Assembly
8,238
236sqmi
(611km)
|
Bond County
005
Greenville
1817
Crawford County, Edwards County, and Madison County
Shadrach Bond(1773–1832), FirstGovernor of Illinois
17,768
380sqmi
(984km)
|
Boone County
007
Belvidere
1837
Winnebago County
Daniel Boone(1734-1820), trailblazer of theWilderness Roadin Kentucky
54,165
281sqmi
(728km)
|
Brown County
009
Mount Sterling
1839
Schuyler County
Jacob Brown(1775–1828), a successfulAmerican Revolutionarmy officer responsible for Great Lakes defenses
6,937
306sqmi
(793km)
|
Bureau County
011
Princeton
1837
Putnam County
Pierre de Bureo, Frenchman,North American fur trader
34,978
869sqmi
(2,251km)
|
Calhoun County
013
Hardin
1825
Pike County
John C. Calhoun(1782–1850),South Carolinasenator and seventhVice President of the United States
5,089
254sqmi
(658km)
|
Carroll County
015
Mount Carroll
1839
Jo Daviess
Charles Carroll of Carrollton(1737–1832), signed theDeclaration of Independenceon behalf ofMaryland
15,387
444sqmi
(1,150km)
|
Cass County
017
Virginia
1837
Morgan County
Lewis Cass(1782–1866), second governor ofMichigan Territory, fourteenthUnited States Secretary of War
13,642
376sqmi
(974km)
|
Champaign County
019
Urbana
1833
Vermilion County
Champaign County, Ohio, which took its name from theFrenchfor "open level country"
201,081
997sqmi
(2,582km)
|
Christian County
021
Taylorville
1839
Sangamon County
Christian County, Kentucky, which was itself named afterColonel William Christian
34,800
709sqmi
(1,836km)
|
Clark County
023
Marshall
1819
Crawford County
George Rogers Clark(1752–1818), highest-ranking officer in theNorthwest Territoryduring theAmerican Revolution
16,335
502sqmi
(1,300km)
|
Clay County
025
Louisville
1824
Wayne, Lawrence, Fayette, and Crawford County
Henry Clay(1777–1852), Kentucky legislator who negotiated theMissouri Compromise
13,815
469sqmi
(1,215km)
|
Clinton County
027
Carlyle
1824
Washington, Bond, and Fayette County
DeWitt Clinton(1769–1828),Governor of New York, responsible for the construction of theErie Canal
37,762
474sqmi
(1,228km)
|
Coles County
029
Charleston
1830
Clark and Edgar County
Edward Coles(1786–1868), secondGovernor of Illinois, responsible for the abolition of slavery in Illinois
53,873
508sqmi
(1,316km)
|
Cook County
031
Chicago
1831
Putnam County
Daniel Pope Cook(1794–1827), politician and firstAttorney General of Illinois
5,194,675
946sqmi
(2,450km)
|
Crawford County
033
Robinson
1816
Edwards County
William H. Crawford(1772–1834), ninthUnited States Secretary of War, seventhSecretary of the Treasury
19,817
444sqmi
(1,150km)
|
Cumberland County
035
Toledo
1843
Coles County
Disputed:Cumberland Road, which entered the county;Cumberland, Maryland; orCumberland Riverin Kentucky
11,048
346sqmi
(896km)
|
DeKalb County
037
Sycamore
1837
Kane County
Johann de Kalb(1721–80), German soldier in theContinental Armywho fought alongsideGilbert du Motier, marquis de Lafayette
105,160
634sqmi
(1,642km)
|
DeWitt County
039
Clinton
1839
Macon and McLean County
DeWitt Clinton(1769–1828),Governor of New York, responsible for the construction of theErie Canal
16,561
398sqmi
(1,031km)
|
Douglas County
041
Tuscola
1859
Coles County
Stephen A. Douglas(1813–61), prominent Illinois Democrat whoengaged in debateswithAbraham Lincoln
19,980
417sqmi
(1,080km)
|
DuPage County
043
Wheaton
1839
Cook County
DuPage River
916,924
334sqmi
(865km)
|
Edgar County
045
Paris
1823
Clark County
John Edgar(c. 1750–1832), Illinois delegate to theNorthwest Territorylegislature; at time, wealthiest man in Illinois
18,576
624sqmi
(1,616km)
|
Edwards County
047
Albion
1814
Gallatin County and Madison County
Ninian Edwards(1775–1833), thirdGovernor of the State of Illinoisand only governor of theIllinois Territory
6,721
222sqmi
(575km)
|
Effingham County
049
Effingham
1831
Fayette and Crawford County
Lord Thomas Effingham, military officer who resigned from theBritish Armyto avoid fighting the American colonies
34,242
479sqmi
(1,241km)
|
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 theAmericanandFrench Revolutions.
22,140
716sqmi
(1,854km)
|
Ford County
053
Paxton
1859
Vermilion County
Thomas Ford(1800–50), eighthGovernor of Illinois; served during theIllinois Mormon War
14,081
486sqmi
(1,259km)
|
Franklin County
055
Benton
1818
White County and Gallatin County
Benjamin Franklin(1706–90), prolific writer, inventor, and politician; key factor in theAmerican Revolution
39,561
412sqmi
(1,067km)
|
Fulton County
057
Lewistown
1823
Pike County
Robert Fulton(1765–1815), inventor of thesteamboat
37,069
866sqmi
(2,243km)
|
Gallatin County
059
Shawneetown
1812
Randolph County
Albert Gallatin(1761–1849), fourth and longest-servingUnited States Secretary of the Treasury
5,589
324sqmi
(839km)
|
Greene County
061
Carrollton
1821
Madison County
Nathanael Greene(1742–86), major general in theContinental Army
13,886
543sqmi
(1,406km)
|
Grundy County
063
Morris
1841
LaSalle County
Felix Grundy(1777–1840),Tennesseansenator that served as the thirteenthUnited States Attorney General
50,063
420sqmi
(1,088km)
|
Hamilton County
065
McLeansboro
1821
White County
Alexander Hamilton(1755–1804), firstUnited States Secretary of the Treasury
8,457
435sqmi
(1,127km)
|
Hancock County
067
Carthage
1825
Adams County
John Hancock(1737–93), first governor of theMassachusetts colonyand president of theSecond Continental Congress
19,104
795sqmi
(2,059km)
|
Hardin County
069
Elizabethtown
1839
Pope County
Hardin County, Kentucky, which was itself named afterJohn Hardin
4,320
178sqmi
(461km)
|
Henderson County
071
Oquawka
1841
Warren County
Henderson County, Kentucky, which was itself named afterRichard Henderson
7,331
379sqmi
(982km)
|
Henry County
073
Cambridge
1825
Fulton County
Patrick Henry(1736-99),American Revolutionary Warfigure and first and sixthGovernor of Virginia
50,486
823sqmi
(2,132km)
|
Iroquois County
075
Watseka
1833
Vermilion County
IroquoisNative Americans
29,718
1,116sqmi
(2,890km)
|
Jackson County
077
Murphysboro
1816
Randolph County and Johnson County
Andrew Jackson(1767-1845), seventhPresident of the United States, United States Senator fromTennessee, and general in theWar of 1812
60,218
588sqmi
(1,523km)
|
Jasper County
079
Newton
1831
Clay and Crawford County
Sgt.William Jasper(c. 1750-79),American Revolutionary Warsoldier popularized byParson Weems
9,698
494sqmi
(1,279km)
|
Jefferson County
081
Mount Vernon
1819
Edwards and White County
Thomas Jefferson(1743-1826), thirdPresident of the United States, secondVice President of the United States,Governor of Virginia, and one of the foremostFounding Fathers of the United States
38,827
571sqmi
(1,479km)
|
Jersey County
083
Jerseyville
1839
Greene County
State ofNew Jersey, from which many early settlers hailed
22,985
369sqmi
(956km)
|
Jo Daviess County
085
Galena
1827
Henry, Mercer, and Putnam County
Joseph Hamilton Daveiss(1774-1811), commander of the Indiana Dragoons at theBattle of Tippecanoe
22,678
601sqmi
(1,557km)
|
Johnson County
087
Vienna
1812
Randolph County
Richard Mentor Johnson(abt. 1780-1850), ninthVice President of the United Statesand United States Senator formKentucky
12,582
346sqmi
(896km)
|
Kane County
089
Geneva
1836
LaSalle County
Elias Kane(1794-1835), United States Senator fromIllinois
515,269
521sqmi
(1,349km)
|
Kankakee County
091
Kankakee
1853
Iroquois and Will County
Kankakee River
113,449
678sqmi
(1,756km)
|
Kendall County
093
Yorkville
1841
LaSalle and Kane County
Amos Kendall(1789-1869),United States Postmaster Generalunder PresidentsAndrew JacksonandMartin Van Buren
114,736
321sqmi
(831km)
|
Knox County
095
Galesburg
1825
Fulton County
Gen.Henry Knox(1750-1806),American Revolutionary Wargeneral and firstUnited States Secretary of War
52,919
716sqmi
(1,854km)
|
Lake County
097
Waukegan
1839
McHenry County
Lake Michigan
703,462
448sqmi
(1,160km)
|
LaSalle County
099
Ottawa
1831
Putnam and Tazewell County
Sieur de la Salle(1643-87), French explorer of theGreat Lakes.
113,924
1,135sqmi
(2,940km)
|
Lawrence County
101
Lawrenceville
1821
Crawford and Edwards County
Capt.James Lawrence(1781-1813), commander of theUSSChesapeakein theWar of 1812. Famous for his command "Don't give up the ship!"
16,833
372sqmi
(963km)
|
Lee County
103
Dixon
1839
Ogle County
"Light Horse"Henry Lee III(1756-1818),American Revolutionary Warofficer and ninthGovernor of Virginia
36,031
725sqmi
(1,878km)
|
Livingston County
105
Pontiac
1837
LaSalle and McLean County
Edward Livingston(1764-1836), prominent jurist, Congressman fromNew YorkandLouisiana, andU.S. Secretary of Statefrom 1831-33.
38,950
1,044sqmi
(2,704km)
|
Logan County
107
Lincoln
1839
Sangamon County
John Logan, a country doctor and early settler, and the father ofJohn A. Logan.
30,305
618sqmi
(1,601km)
|
Macon County
115
Decatur
1829
Shelby County
Nathaniel Macon(1758-1837), sixthSpeaker of the United States House of RepresentativesandUnited States SenatorfromNorth Carolina.
110,768
581sqmi
(1,505km)
|
Macoupin County
117
Carlinville
1829
Greene County
Native American wordMacoupin, meaningAmerican lotus
47,765
864sqmi
(2,238km)
|
Madison County
119
Edwardsville
1812
St. Clair County and Randolph County
James Madison(1751-1836), fourthPresident of the United Statesand principal author of theConstitution of the United States.
269,282
725sqmi
(1,878km)
|
Marion County
121
Salem
1823
Fayette and Jefferson County
Francis Marion(c. 1732-95), general in theAmerican Revolutionary Warknown as "The Swamp Fox"
39,437
572sqmi
(1,481km)
|
Marshall County
123
Lacon
1839
Putnam County
John Marshall (1755-1835), fourth and longest-servingChief Justice of the United States, wrote opinion inMarbury v. Madisonestablishing the principle ofjudicial review
12,640
386sqmi
(1,000km)
|
Mason County
125
Havana
1841
Tazewell and Menard County
Named afterMason County, Kentucky, itself named afterGeorge Mason
14,666
539sqmi
(1,396km)
|
Massac County
127
Metropolis
1843
Pope and Johnson County
Fort Massac, a colonial-era fort on theOhio River
15,429
239sqmi
(619km)
|
McDonough County
109
Macomb
1826
Schuyler County
CommodoreThomas Macdonough(1783-1825), commander of American naval forces at theBattle of Plattsburgh
32,612
589sqmi
(1,526km)
|
McHenry County
111
Woodstock
1836
Cook and LaSalle County
MajorWilliam McHenry(c. 1771-1835), officer in during several campaigns againstNative Americansand member of the Illinois legislature
308,760
604sqmi
(1,564km)
|
McLean County
113
Bloomington
1830
Tazewell County
John McLean(1791-1830),United States RepresentativeandUnited States Senatorfrom Illinois (the latter from 1824-25 and 1829-30)
169,572
1,184sqmi
(3,067km)
|
Menard County
129
Petersburg
1839
Sangamon County
Pierre Menard(1766-1844), prominent early settler and firstLieutenant Governor of Illinois
12,705
314sqmi
(813km)
|
Mercer County
131
Aledo
1825
Schuyler County
Hugh Mercer(1726-77), British officer in theSeven Years' Warand general in theContinental Armyduring theAmerican Revolutionary War
16,434
561sqmi
(1,453km)
|
Monroe County
133
Waterloo
1816
Randolph County and St. Clair County
James Monroe(1758-1831), seventhUnited States Secretary of State, eighthUnited States Secretary of War,Governor of Virginia, and fifthPresident of the United States
32,957
388sqmi
(1,005km)
|
Montgomery County
135
Hillsboro
1821
Bond and Madison County
Gen.Richard Montgomery(1738-75), brigadier-general in theContinental Armywho led the unsuccessfulinvasion of Canada
30,104
704sqmi
(1,823km)
|
Morgan County
137
Jacksonville
1823
Sangamon County
Gen.Daniel Morgan(1736-1802), successful tactician in theAmerican Revolutionary Warand laterUnited States RepresentativefromVirginia
35,547
569sqmi
(1,474km)
|
Moultrie County
139
Sullivan
1843
Shelby and Macon County
Gen.William Moultrie(1730-1805),American Revolutionary Wargeneral andGovernor of South Carolina
14,846
336sqmi
(870km)
|
Ogle County
141
Oregon
1836
Jo Daviess
Joseph Ogle(1737-1821), early settler in southwest Illinois, who helped found the firstMethodistchurch in Illinois
53,497
759sqmi
(1,966km)
|
Peoria County
143
Peoria
1825
Fulton County
ThePeoriaNative American tribe
186,494
620sqmi
(1,606km)
|
Perry County
145
Pinckneyville
1827
Randolph and Jackson County
CommodoreOliver Hazard Perry(1785-1819), American naval officer who led the victorious American forces at theBattle of Lake Erie
22,350
441sqmi
(1,142km)
|
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
16,729
440sqmi
(1,140km)
|
Pike County
149
Pittsfield
1821
Madison, Bond, and Clark County
Zebulon Pike(1779-1813), early explorer of theAmerican Southwest, namesake ofPikes Peak
16,430
830sqmi
(2,150km)
|
Pope County
151
Golconda
1816
Gallatin and Johnson County
Nathaniel Pope(1784-1850), early Delegate fromIllinois Territoryto Congress and judge on theUnited States District Court for the District of Illinois
4,470
371sqmi
(961km)
|
Pulaski County
153
Mound City
1843
Alexander and Johnson County
Gen.Casimir Pulaski(1745-79),Polish Americangeneral of cavalry in theAmerican Revolutionary War
6,161
201sqmi
(521km)
|
Putnam County
155
Hennepin
1825
Fulton County
Gen.Israel Putnam(1718-90), commander of American forces at theBattle of Bunker Hill
6,006
160sqmi
(414km)
|
Randolph County
157
Chester
1795
St. Clair County
Edmund Randolph(1753-1813), firstAttorney General of the United States, and brieflyUnited States Secretary of State
33,476
578sqmi
(1,497km)
|
Richland County
159
Olney
1841
Clay and Lawrence County
Richland County, Ohio, itself named for its richsoil
16,233
360sqmi
(932km)
|
Rock Island County
161
Rock Island
1831
Jo Daviess County
Rock Island
147,546
427sqmi
(1,106km)
|
Saline County
165
Harrisburg
1847
Gallatin County
Salt springs within the county
24,913
383sqmi
(992km)
|
Sangamon County
167
Springfield
1821
Madison and Bond County
Sangamon River
197,465
868sqmi
(2,248km)
|
Schuyler County
169
Rushville
1825
Pike and Fulton County
Gen.Philip Schuyler(1733-1804),American Revolutionary Wargeneral andUnited States SenatorfromNew York
7,544
437sqmi
(1,132km)
|
Scott County
171
Winchester
1839
Morgan County
Scott County, Kentucky, itself named afterCharles Scott
5,355
251sqmi
(650km)
|
Shelby County
173
Shelbyville
1827
Fayette County
Isaac Shelby(1750-1826), soldier in theAmerican Revolutionary WarandWar of 1812, and first and fifthGovernor of Kentucky
22,363
759sqmi
(1,966km)
|
St. Clair County
163
Belleville
1790
original two counties
Arthur St. Clair(1737-1818), major general in theAmerican Revolutionary Warand first Governor of theNorthwest Territory
270,056
664sqmi
(1,720km)
|
Stark County
175
Toulon
1839
Knox and Putnam County
Gen.John Stark(1728-1822), general in theAmerican Revolutionary War, called the "Hero ofBennington"
5,994
288sqmi
(746km)
|
Stephenson County
177
Freeport
1837
Jo Daviess and Winnebago County
Benjamin Stephenson(1769-1822), representative ofIllinois Territoryin theUnited States Congressfrom 1814 to 1816
47,711
564sqmi
(1,461km)
|
Tazewell County
179
Pekin
1827
Sangamon County
Littleton Waller Tazewell(1774-1860), United States Senator from (and later governor of)Virginia
135,394
649sqmi
(1,681km)
|
Union County
181
Jonesboro
1818
Johnson County
The federal union of the states
17,808
416sqmi
(1,077km)
|
Vermilion County
183
Danville
1826
Edgar County
TheVermilion River
81,625
899sqmi
(2,328km)
|
Wabash County
185
Mount Carmel
1824
Edwards County
TheWabash River
11,947
224sqmi
(580km)
|
Warren County
187
Monmouth
1825
Schuyler County
Joseph Warren(1741-75), played a role inAmerican Patriotmovements, a prominent early fatality in theAmerican Revolutionary War
17,707
543sqmi
(1,406km)
|
Washington County
189
Nashville
1818
St. Clair County
George Washington(1732-99), commander-in-chief of American forces in theAmerican Revolutionary Warand firstPresident of the United States
14,716
563sqmi
(1,458km)
|
Wayne County
191
Fairfield
1819
Edwards County
Gen. "Mad"Anthony Wayne(1745-96),major generalin the United States Army in theAmerican Revolutionary Warand theNorthwest Indian War
16,760
714sqmi
(1,849km)
|
White County
193
Carmi
1815
Gallatin County
Isaac White(1776-1811), resident of Illinois who enlisted in the Indiana militia and was killed at theBattle of Tippecanoe
14,665
495sqmi
(1,282km)
|
Whiteside County
195
Morrison
1836
Jo Daviess and Henry County
Samuel Whiteside(1783-1868), state legislator and militia leader
58,498
685sqmi
(1,774km)
|
Will County
197
Joliet
1836
Cook and Iroquois County
Conrad Will(1779-1835),physician, local businessman and longtime member of the state legislature
677,560
837sqmi
(2,168km)
|
Williamson County
199
Marion
1839
Franklin County
Hugh Williamson(1735-1819), delegate fromNorth Carolinato thePhiladelphia Convention
66,357
424sqmi
(1,098km)
|
Winnebago County
201
Rockford
1836
Jo Daviess
WinnebagoNative Americans
295,266
514sqmi
(1,331km)
|
Woodford County
203
Eureka
1841
Tazewell and McLean County
Gen.William Woodford(1734-80), brigadier general in theAmerican Revolutionary Warwho died while a British prisoner
38,664
528sqmi
(1,368km)
|
