Counties of Illinois

Counties of Illinois
US Census, Ruhrfisch · Public domain · source
Name	Counties of Illinois
Caption	Map of Illinois counties
Territory	Illinois
Current number	102
Population range	Adams County — Cook County
Area range	Putnam County — Cook County

Counties of Illinois The counties of Illinois are 102 administrative and political subdivisions that include historic seats such as Springfield, economic centers like Chicago, and cultural hubs including Peoria and Rockford. They were established across the 18th and 19th centuries amid territorial changes involving Northwest Territory, Indiana Territory, and events such as the Black Hawk War and the implementation of the Northwest Ordinance. County seats, courthouses, and county boards interconnect with institutions such as the Illinois General Assembly, University of Illinois Urbana-Champaign, Southern Illinois University Carbondale, and federal entities like the United States Census Bureau.

History

County formation in Illinois traces to the early settlement patterns influenced by the French colonization of the Americas, the Treaty of Greenville, and land cessions after the War of 1812. Early counties such as St. Clair County and Gallatin County were created as populations expanded along the Mississippi River, Ohio River, and routes used during the Great Migration. Legislative actions by the Illinois General Assembly and judicial precedents from the Illinois Supreme Court defined boundaries, while surveying techniques from figures associated with the Public Land Survey System influenced township layouts. Disputes over boundaries involved neighboring states and events like the Toledo War precedent and decisions informed by the United States Supreme Court.

Geography and demographics

Illinois counties span diverse physiographic provinces including the Central Lowland, the Cahokia Mounds region, and the Shawnee National Forest in the south. Counties along the Lake Michigan shore such as Cook County host dense urban populations tied to the Chicago metropolitan area and institutions like Northwestern University and University of Chicago, while counties such as Alexander County exhibit rural demographics with ties to agriculture served by USDA programs. Demographic shifts tracked by the United States Census Bureau reflect migration linked to events including the Industrial Revolution, the Great Migration, and modern changes influenced by policies from the Department of Housing and Urban Development. Major transportation corridors including Interstate 55, Interstate 57, and Interstate 80 shape settlement patterns and link counties to markets such as St. Louis, Indianapolis, and Milwaukee.

Government and administration

Each county operates under statutory frameworks enacted by the Illinois General Assembly and decisions of the Illinois Supreme Court and interacts with federal agencies such as the Internal Revenue Service and the Federal Emergency Management Agency. County governance commonly includes offices like the county board, county clerk, sheriff, and state's attorney; these offices coordinate with entities such as the Illinois State Police and local municipalities including Chicago and Aurora. Budgetary oversight and taxation involve the Illinois Comptroller and property assessment practices shaped by cases heard in the Illinois Appellate Court. Intergovernmental cooperation includes participation in regional agencies such as the Chicago Metropolitan Agency for Planning and collaborations with organizations like the Illinois Association of County Board Members.

Economy and infrastructure

County economies reflect sectors anchored in agriculture, manufacturing, services, and transportation. Rural counties produce commodities under programs of the United States Department of Agriculture, while urban counties host headquarters for firms listed on the NASDAQ and the New York Stock Exchange and institutions such as AbbVie, Boeing, and Walgreens Boots Alliance. Infrastructure includes O'Hare International Airport, rail corridors operated by Union Pacific Railroad and BNSF Railway, and river ports along the Mississippi River and Illinois River connected to the Port of Chicago. Economic development agencies, including the Illinois Department of Commerce and Economic Opportunity, coordinate incentives and workforce programs often aligned with Community College Districts and universities like Southern Illinois University and Illinois State University.

List of counties

Adams County; Alexander County; Bond County; Boone County; Brown County; Bureau County; Calhoun County; Carroll County; Cass County; Champaign County; Christian County; Clark County; Clay County; Clinton County; Coles County; Cook County; Crawford County; Cumberland County; DeKalb County; DeWitt County; Douglas County; DuPage County; Edgar County; Edwards County; Effingham County; Fayette County; Ford County; Franklin County; Fulton County; Gallatin County; Greene County; Grundy County; Hamilton County; Hancock County; Hardin County; Henderson County; Henry County; Iroquois County; Jackson County; Jasper County; Jefferson County; Jersey County; Jo Daviess County; Johnson County; Kane County; Kankakee County; Kendall County; Knox County; LaSalle County; Lake County; Lawrence County; Lee County; Livingston County; Logan County; McDonough County; McHenry County; McLean County; Macon County; Macoupin County; Madison County; Marion County; Marshall County; Mason County; Massac County; Menard County; Mercer County; Monroe County; Montgomery County; Morgan County; Moultrie County; Ogle County; Peoria County; Perry County; Piatt County; Pike County; Pope County; Pulaski County; Putnam County; Randolph County; Richland County; Rock Island County; Saline County; Sangamon County; Schuyler County; Scott County; Shelby County; St. Clair County; Stark County; Stephenson County; Tazewell County; Union County; Vermilion County; Wabash County; Warren County; Washington County; Wayne County; White County; Whiteside County; Will County; Williamson County; Winnebago County; Woodford County.

Former and renamed counties

Historic entities include former counties and renamings such as Illinois County, Virginia antecedents, adjustments stemming from territorial realignments after the Louisiana Purchase and the Adams-Onís Treaty, and suppressed counties affected by court rulings of the Illinois Supreme Court. Examples from early statehood included provisional jurisdictions reorganized during the eras of Territory of Michigan and Indiana Territory administration; names and boundaries changed in legislative acts by the Illinois General Assembly as populations and transportation patterns evolved. St. Clair County and Gallatin County represent enduring names, while other designations were consolidated or absorbed to form many of the modern 102 counties recognized by the United States Census Bureau.

Category:Illinois counties