List of counties in Illinois

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.

Counties of Illinois
LocationState of Illinois
Number102
Populations3,597 (Hardin) – 5,109,292 (Cook)
Areas172 square miles (450 km2) (Putnam) – 1,186 square miles (3,070 km2) (McLean)
Government
Subdivisions

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.

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.

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[5] Area[2] Map
Adams County 001 Quincy1825Pike CountyJohn Quincy Adams (1767–1848), sixth President of the United States 64,725 855 sq mi
(2,214 km2)		State map highlighting Adams County
Alexander County 003 Cairo1819Union CountyWilliam M. Alexander, settler and state representative in the Illinois General Assembly 4,858 236 sq mi
(611 km2)		State map highlighting Alexander County
Bond County 005 Greenville1817Crawford County, Edwards County, and Madison CountyShadrach Bond (1773–1832), first Governor of Illinois 16,566 380 sq mi
(984 km2)		State map highlighting Bond County
Boone County 007 Belvidere1837Winnebago CountyDaniel Boone (1734–1820), trailblazer of the Wilderness Road in Kentucky 53,154 280 sq mi
(725 km2)		State map highlighting Boone County
Brown County 009 Mount Sterling1839Schuyler CountyJacob Brown (1775–1828), successful War of 1812 army officer responsible for Great Lakes defenses 6,330 305 sq mi
(790 km2)		State map highlighting Brown County
Bureau County 011 Princeton1837Putnam CountyPierre de Bureo, Frenchman, North American fur trader 32,828 869 sq mi
(2,251 km2)		State map highlighting Bureau County
Calhoun County 013 Hardin1825Pike CountyJohn C. Calhoun (1782–1850), South Carolina senator and seventh Vice President of the United States 4,360 253 sq mi
(655 km2)		State map highlighting Calhoun County
Carroll County 015 Mount Carroll1839Jo DaviessCharles Carroll of Carrollton (1737–1832), signed the Declaration of Independence on behalf of Maryland 15,529 445 sq mi
(1,153 km2)		State map highlighting Carroll County
Cass County 017 Virginia1837Morgan CountyLewis Cass (1782–1866), second governor of Michigan Territory, fourteenth United States Secretary of War 12,657 375 sq mi
(971 km2)		State map highlighting Cass County
Champaign County 019 Urbana1833Vermilion CountyChampaign County, Ohio, which took its name from the French for "open level country" 206,542 996 sq mi
(2,580 km2)		State map highlighting Champaign County
Christian County 021 Taylorville1839Sangamon CountyChristian County, Kentucky, which was named after William Christian 33,436 709 sq mi
(1,836 km2)		State map highlighting Christian County
Clark County 023 Marshall1819Crawford CountyGeorge Rogers Clark (1752–1818), highest-ranking officer in the Northwest Territory during the American Revolution 15,229 501 sq mi
(1,298 km2)		State map highlighting Clark County
Clay County 025 Louisville1824Wayne, Lawrence, Fayette, and Crawford CountyHenry Clay (1777–1852), Kentucky legislator who negotiated the Missouri Compromise 13,047 468 sq mi
(1,212 km2)		State map highlighting Clay County
Clinton County 027 Carlyle1824Washington, Bond, and Fayette CountyDeWitt Clinton (1769–1828), Governor of New York, responsible for the construction of the Erie Canal 36,909 474 sq mi
(1,228 km2)		State map highlighting Clinton County
Coles County 029 Charleston1830Clark and Edgar CountyEdward Coles (1786–1868), second Governor of Illinois, responsible for the abolition of slavery in Illinois 46,334 508 sq mi
(1,316 km2)		State map highlighting Coles County
Cook County 031 Chicago1831Putnam CountyDaniel Pope Cook (1794–1827), politician and first Attorney General of Illinois 5,109,292 944 sq mi
(2,445 km2)		State map highlighting Cook County
Crawford County 033 Robinson1816Edwards CountyWilliam H. Crawford (1772–1834), ninth United States Secretary of War, seventh Secretary of the Treasury 18,536 443 sq mi
(1,147 km2)		State map highlighting Crawford County
Cumberland County 035 Toledo1843Coles CountyDisputed: Cumberland Road, which entered the county; Cumberland, Maryland; or Cumberland River in Kentucky 10,324 345 sq mi
(894 km2)		State map highlighting Cumberland County
DeKalb County 037 Sycamore1837Kane CountyJohann de Kalb (1721–1780), German officer in the Continental Army who fought alongside Gilbert du Motier, marquis de Lafayette 100,232 631 sq mi
(1,634 km2)		State map highlighting DeKalb County
DeWitt County 039 Clinton1839Macon and McLean CountyDeWitt Clinton (1769–1828), Governor of New York, responsible for the construction of the Erie Canal 15,310 397 sq mi
(1,028 km2)		State map highlighting DeWitt County
Douglas County 041 Tuscola1859Coles CountyStephen A. Douglas (1813–1861), prominent Illinois Democrat who engaged in debates with Abraham Lincoln 19,755 416 sq mi
(1,077 km2)		State map highlighting Douglas County
DuPage County 043 Wheaton1839Cook CountyDuPage River 920,901 327 sq mi
(847 km2)		State map highlighting DuPage County
Edgar County 045 Paris1823Clark CountyJohn Edgar (c. 1750–1832), Illinois delegate to the Northwest Territory legislature; at the time, wealthiest man in Illinois 16,433 623 sq mi
(1,614 km2)		State map highlighting Edgar County
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 6,071 222 sq mi
(575 km2)		State map highlighting Edwards County
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 34,325 478 sq mi
(1,238 km2)		State map highlighting Effingham County
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. 21,305 716 sq mi
(1,854 km2)		State map highlighting Fayette County
Ford County 053 Paxton1859Vermilion CountyThomas Ford (1800–1850), eighth Governor of Illinois; served during the Illinois Mormon War 13,249 485 sq mi
(1,256 km2)		State map highlighting Ford County
Franklin County 055 Benton1818White County and Gallatin CountyBenjamin Franklin (1706–1790), prolific writer, inventor, and politician; key factor in the American Revolution 37,242 408 sq mi
(1,057 km2)		State map highlighting Franklin County
Fulton County 057 Lewistown1823Pike CountyRobert Fulton (1765–1815), inventor of the steamboat 33,021 865 sq mi
(2,240 km2)		State map highlighting Fulton County
Gallatin County 059 Shawneetown1812Randolph CountyAlbert Gallatin (1761–1849), fourth and longest-serving United States Secretary of the Treasury 4,855 322 sq mi
(834 km2)		State map highlighting Gallatin County
Greene County 061 Carrollton1821Madison CountyNathanael Greene (1742–1786), major general in the Continental Army 11,651 543 sq mi
(1,406 km2)		State map highlighting Greene County
Grundy County 063 Morris1841LaSalle CountyFelix Grundy (1777–1840), Tennessean senator who served as the thirteenth United States Attorney General 53,041 418 sq mi
(1,083 km2)		State map highlighting Grundy County
Hamilton County 065 McLeansboro1821White CountyAlexander Hamilton (1755–1804), first United States Secretary of the Treasury 7,984 434 sq mi
(1,124 km2)		State map highlighting Hamilton County
Hancock County 067 Carthage1825Adams CountyJohn Hancock (1737–1793), first governor of the Massachusetts colony and president of the Second Continental Congress 17,244 793 sq mi
(2,054 km2)		State map highlighting Hancock County
Hardin County 069 Elizabethtown1839Pope CountyHardin County, Kentucky, which was named after John Hardin 3,597 177 sq mi
(458 km2)		State map highlighting Hardin County
Henderson County 071 Oquawka1841Warren CountyHenderson County, Kentucky, which was named after Richard Henderson 6,151 378 sq mi
(979 km2)		State map highlighting Henderson County
Henry County 073 Cambridge1825Fulton CountyPatrick Henry (1736–1799), American Revolutionary War figure; first and sixth Governor of Virginia 48,419 822 sq mi
(2,129 km2)		State map highlighting Henry County
Iroquois County 075 Watseka1833Vermilion CountyIroquois Native Americans 26,473 1,117 sq mi
(2,893 km2)		State map highlighting Iroquois County
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 52,617 584 sq mi
(1,513 km2)		State map highlighting Jackson County
Jasper County 079 Newton1831Clay and Crawford CountySgt. William Jasper (c. 1750–1779), American Revolutionary War soldier popularized by Parson Weems 9,212 494 sq mi
(1,279 km2)		State map highlighting Jasper County
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 36,400 571 sq mi
(1,479 km2)		State map highlighting Jefferson County
Jersey County 083 Jerseyville1839Greene CountyState of New Jersey, from which many early settlers hailed 21,246 369 sq mi
(956 km2)		State map highlighting Jersey County
Jo Daviess County 085 Galena1827Henry, Mercer, and Putnam CountyJoseph Hamilton Daveiss (1774–1811), commander of the Indiana Dragoons at the Battle of Tippecanoe 21,758 600 sq mi
(1,554 km2)		State map highlighting Jo Daviess County
Johnson County 087 Vienna1812Randolph CountyRichard Mentor Johnson (c. 1780–1850), ninth Vice President of the United States and United States Senator from Kentucky 13,381 343 sq mi
(888 km2)		State map highlighting Johnson County
Kane County 089 Geneva1836LaSalle CountyElias Kane (1794–1835), United States Senator from Illinois 514,182 519 sq mi
(1,344 km2)		State map highlighting Kane County
Kankakee County 091 Kankakee1853Iroquois and Will CountyKankakee River 106,074 676 sq mi
(1,751 km2)		State map highlighting Kankakee County
Kendall County 093 Yorkville1841LaSalle and Kane CountyAmos Kendall (1789–1869), United States Postmaster General under Presidents Andrew Jackson and Martin Van Buren 137,254 320 sq mi
(829 km2)		State map highlighting Kendall County
Knox County 095 Galesburg1825Fulton CountyGen. Henry Knox (1750–1806), American Revolutionary War general and first United States Secretary of War 48,640 716 sq mi
(1,854 km2)		State map highlighting Knox County
Lake County 097 Waukegan1839McHenry CountyLake Michigan 709,150 443 sq mi
(1,147 km2)		State map highlighting Lake County
LaSalle County 099 Ottawa1831Putnam and Tazewell CountySieur de la Salle (1643–1687), French explorer of the Great Lakes 108,078 1,135 sq mi
(2,940 km2)		State map highlighting LaSalle County
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!" 14,914 372 sq mi
(963 km2)		State map highlighting Lawrence County
Lee County 103 Dixon1839Ogle County"Light Horse" Henry Lee III (1756–1818), American Revolutionary War officer and ninth Governor of Virginia 33,848 724 sq mi
(1,875 km2)		State map highlighting Lee County
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 35,521 1,043 sq mi
(2,701 km2)		State map highlighting Livingston County
Logan County 107 Lincoln1839Sangamon CountyJohn Logan, country doctor and early settler, and the father of John A. Logan 27,591 618 sq mi
(1,601 km2)		State map highlighting Logan County
Macon County 115 Decatur1829Shelby CountyNathaniel Macon (1758–1837), sixth Speaker of the United States House of Representatives and United States Senator from North Carolina 101,483 580 sq mi
(1,502 km2)		State map highlighting Macon County
Macoupin County 117 Carlinville1829Greene CountyNative American word macoupin, meaning "American lotus" 44,245 862 sq mi
(2,233 km2)		State map highlighting Macoupin County
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 263,864 716 sq mi
(1,854 km2)		State map highlighting Madison County
Marion County 121 Salem1823Fayette and Jefferson CountyFrancis Marion (c. 1732–1795), general in the American Revolutionary War known as "The Swamp Fox" 36,914 572 sq mi
(1,481 km2)		State map highlighting Marion County
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 11,678 386 sq mi
(1,000 km2)		State map highlighting Marshall County
Mason County 125 Havana1841Tazewell and Menard CountyNamed after Mason County, Kentucky, itself named after George Mason 12,748 539 sq mi
(1,396 km2)		State map highlighting Mason County
Massac County 127 Metropolis1843Pope and Johnson CountyFort Massac, a colonial-era fort on the Ohio River 13,896 237 sq mi
(614 km2)		State map highlighting Massac County
McDonough County 109 Macomb1826Schuyler CountyCommodore Thomas Macdonough (1783–1825), commander of American naval forces at the Battle of Plattsburgh 26,861 589 sq mi
(1,526 km2)		State map highlighting McDonough County
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 311,747 603 sq mi
(1,562 km2)		State map highlighting McHenry County
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) 171,141 1,183 sq mi
(3,064 km2)		State map highlighting McLean County
Menard County 129 Petersburg1839Sangamon CountyPierre Menard (1766–1844), prominent early settler and first Lieutenant Governor of Illinois 12,121 314 sq mi
(813 km2)		State map highlighting Menard County
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 15,504 561 sq mi
(1,453 km2)		State map highlighting Mercer County
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 35,033 385 sq mi
(997 km2)		State map highlighting Monroe County
Montgomery County 135 Hillsboro1821Bond and Madison CountyGen. Richard Montgomery (1738–1775), brigadier-general in the Continental Army who led the unsuccessful invasion of Canada 28,020 703 sq mi
(1,821 km2)		State map highlighting Montgomery County
Morgan County 137 Jacksonville1823Sangamon CountyGen. Daniel Morgan (1736–1802), successful tactician in the American Revolutionary War and later United States Representative from Virginia 32,209 568 sq mi
(1,471 km2)		State map highlighting Morgan County
Moultrie County 139 Sullivan1843Shelby and Macon CountyGen. William Moultrie (1730–1805), American Revolutionary War general and Governor of South Carolina 14,323 335 sq mi
(868 km2)		State map highlighting Moultrie County
Ogle County 141 Oregon1836Jo DaviessJoseph Ogle (1737–1821), early settler in southwest Illinois, who helped found the first Methodist church in Illinois 51,351 758 sq mi
(1,963 km2)		State map highlighting Ogle County
Peoria County 143 Peoria1825Fulton CountyThe Peoria Native American tribe 178,383 618 sq mi
(1,601 km2)		State map highlighting Peoria County
Perry County 145 Pinckneyville1827Randolph and Jackson CountyCmdre. Oliver Hazard Perry (1785–1819), American naval officer who led the victorious American forces at the Battle of Lake Erie 20,588 441 sq mi
(1,142 km2)		State map highlighting Perry County
Piatt County 147 Monticello1841DeWitt and Macon CountyJames A. Piatt, the patriarch of a prominent settler family in the early history of the county 16,723 439 sq mi
(1,137 km2)		State map highlighting Piatt County
Pike County 149 Pittsfield1821Madison, Bond, and Clark CountyZebulon Pike (1779–1813), early explorer of the American Southwest, namesake of Pikes Peak 14,484 831 sq mi
(2,152 km2)		State map highlighting Pike County
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 3,770 368 sq mi
(953 km2)		State map highlighting Pope County
Pulaski County 153 Mound City1843Alexander and Johnson CountyGen. Casimir Pulaski (1745–1779), Polish American general of cavalry in the American Revolutionary War 4,991 199 sq mi
(515 km2)		State map highlighting Pulaski County
Putnam County 155 Hennepin1825Fulton CountyGen. Israel Putnam (1718–1790), commander of American forces at the Battle of Bunker Hill 5,572 160 sq mi
(414 km2)		State map highlighting Putnam County
Randolph County 157 Chester1795St. Clair CountyEdmund Randolph (1753–1813), first Attorney General of the United States, and briefly United States Secretary of State 30,068 575 sq mi
(1,489 km2)		State map highlighting Randolph County
Richland County 159 Olney1841Clay and Lawrence CountyRichland County, Ohio, itself named for its rich soil 15,435 360 sq mi
(932 km2)		State map highlighting Richland County
Rock Island County 161 Rock Island1831Jo Daviess CountyRock Island 141,527 427 sq mi
(1,106 km2)		State map highlighting Rock Island County
Saline County 165 Harrisburg1847Gallatin CountyThe Saline River and salt springs in the county 23,087 379 sq mi
(982 km2)		State map highlighting Saline County
Sangamon County 167 Springfield1821Madison and Bond CountySangamon River 194,534 868 sq mi
(2,248 km2)		State map highlighting Sangamon County
Schuyler County 169 Rushville1825Pike and Fulton CountyGen. Philip Schuyler (1733–1804), American Revolutionary War general and United States Senator from New York 6,746 437 sq mi
(1,132 km2)		State map highlighting Schuyler County
Scott County 171 Winchester1839Morgan CountyScott County, Kentucky, itself named after Charles Scott 4,790 250 sq mi
(647 km2)		State map highlighting Scott County
Shelby County 173 Shelbyville1827Fayette CountyIsaac Shelby (1750–1826), soldier in the American Revolutionary War and War of 1812; first and fifth Governor of Kentucky 20,761 758 sq mi
(1,963 km2)		State map highlighting Shelby County
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 252,671 657 sq mi
(1,702 km2)		State map highlighting St. Clair County
Stark County 175 Toulon1839Knox and Putnam CountyGen. John Stark (1728–1822), general in the American Revolutionary War, called the "Hero of Bennington" 5,345 288 sq mi
(746 km2)		State map highlighting Stark County
Stephenson County 177 Freeport1837Jo Daviess and Winnebago CountyBenjamin Stephenson (1769–1822), representative of Illinois Territory in the United States Congress from 1814 to 1816 43,627 564 sq mi
(1,461 km2)		State map highlighting Stephenson County
Tazewell County 179 Pekin1827Sangamon CountyLittleton Waller Tazewell (1774–1860), United States Senator from (and later governor of) Virginia 129,911 646 sq mi
(1,673 km2)		State map highlighting Tazewell County
Union County 181 Jonesboro1818Johnson CountyThe union of the United States 16,767 413 sq mi
(1,070 km2)		State map highlighting Union County
Vermilion County 183 Danville1826Edgar CountyThe Vermilion River 72,337 898 sq mi
(2,326 km2)		State map highlighting Vermilion County
Wabash County 185 Mount Carmel1824Edwards CountyThe Wabash River 11,087 223 sq mi
(578 km2)		State map highlighting Wabash County
Warren County 187 Monmouth1825Schuyler CountyJoseph Warren (1741–1775), played a role in American Patriot movements, a prominent early fatality in the American Revolutionary War 16,354 542 sq mi
(1,404 km2)		State map highlighting Warren County
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 13,643 562 sq mi
(1,456 km2)		State map highlighting Washington County
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 15,872 713 sq mi
(1,847 km2)		State map highlighting Wayne County
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 13,614 494 sq mi
(1,279 km2)		State map highlighting White County
Whiteside County 195 Morrison1836Jo Daviess and Henry CountySamuel Whiteside (1783–1868), state legislator and militia leader 54,658 684 sq mi
(1,772 km2)		State map highlighting Whiteside County
Will County 197 Joliet1836Cook and Iroquois CountyConrad Will (1779–1835),[6] physician, local businessman and longtime member of the state legislature 696,757 835 sq mi
(2,163 km2)		State map highlighting Will County
Williamson County 199 Marion1839Franklin CountyWilliamson County, Tennessee, which was named for Hugh Williamson 66,695 420 sq mi
(1,088 km2)		State map highlighting Williamson County
Winnebago County 201 Rockford1836Jo Daviess CountyWinnebago Native Americans 282,188 513 sq mi
(1,329 km2)		State map highlighting Winnebago County
Woodford County 203 Eureka1841Tazewell and McLean CountyWoodford County, Kentucky, which was named for William Woodford 38,128 527 sq mi
(1,365 km2)		State map highlighting Woodford County

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. "U.S. Census Bureau QuickFacts: Illinois". Retrieved April 2, 2023.
  6. 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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