Adams County (1825 - Present)
Alexander County (1819 - Present)
Allen County Proposed (1841 - 1841)
Audubon County Proposed (1843 - 1843)
Benton County Proposed (1843 - 1843)
Bond County (1817 - Present)
Boone County (1837 - Present)
Brown County (1839 - Present)
Bureau County (1837 - Present)
Calhoun County (1825 - Present)
Carroll County (1839 - Present)
Cass County (1837 - Present)
Champaign County (1833 - Present)
Clark County (1819 - Present)
Clay County (1824 - Present)
Clinton County (1824 - Present)
Coffee County Proposed (1837 - 1837)
Coles County (1830 - Present)
Cook County (1831 - Present)
Crawford County (1816 - Present)
Cumberland County (1843 - Present)
Dane County (1839 - Present)
De Kalb County (1837 - Present)
De Witt County (1839 - Present)
Douglas County (1859 - Present)
Douglas County Proposed (1857 - 1857)
Du Page County (1839 - Present)
Edgar County (1823 - Present)
Edwards County (1814 - Present)
Effingham County (1831 - Present)
Fayette County (1821 - Present)
Ford County (1859 - Present)
Franklin County (1818 - Present)
Fulton County (1823 - Present)
Gallatin County (1812 - Present)
Greene County (1821 - Present)
Grundy County (1841 - Present)
Hamilton County (1821 - Present)
Hancock County (1825 - Present)
Hardin County (1839 - Present)
Harrison County Proposed (1855 - 1855)
Henderson County (1841 - Present)
Henry County (1825 - Present)
Holmes County Proposed (1857 - 1857)
Iroquois County (1833 - Present)
Jackson County (1816 - Present)
Jasper County (1831 - Present)
Jefferson County (1819 - Present)
Jersey County (1839 - Present)
Jo Daviess County (1827 - Present)
Johnson County (1812 - Present)
Kane County (1836 - Present)
Kankakee County (1853 - Present)
Kankakee County Proposed (1851 - 1851)
Kendall County (1841 - Present)
Knox County (1825 - Present)
La Salle County (1831 - Present)
Lake County (1839 - Present)
Lawrence County (1821 - Present)
Lee County (1839 - Present)
Lincoln County Proposed (1867 - 1867)
Livingston County (1837 - Present)
Logan County (1839 - Present)
Macon County (1829 - Present)
Macoupin County (1829 - Present)
Madison County (1812 - Present)
Marion County (1823 - Present)
Marquette County (1843 - 1848)
Marshall County (1839 - Present)
Mason County (1841 - Present)
Massac County (1843 - Present)
Mcdonough County (1826 - Present)
Mchenry County (1836 - Present)
Mclean County (1830 - Present)
Menard County (1839 - Present)
Mercer County (1825 - Present)
Michigan County Proposed (1837 - 1837)
Milton County Proposed (1843 - 1843)
Monroe County (1816 - Present)
Montgomery County (1821 - Present)
Morgan County (1823 - Present)
Moultrie County (1843 - Present)
Ogle County (1836 - Present)
Okaw County Proposed (1841 - 1841)
Oregon County Proposed (1851 - 1851)
Peoria County (1825 - Present)
Perry County (1827 - Present)
Piatt County (1841 - Present)
Pike County (1821 - Present)
Pope County (1816 - Present)
Pulaski County (1843 - Present)
Putnam County (1825 - Present)
Randolph County (1795 - Present)
Richland County (1841 - Present)
Rock Island County (1831 - Present)
Saline County (1847 - Present)
Sangamon County (1821 - Present)
Schuyler County (1825 - Present)
Scott County (1839 - Present)
Shelby County (1827 - Present)
St Clair County (1790 - Present)
Stark County (1839 - Present)
Stephenson County (1837 - Present)
Tazewell County (1827 - Present)
Union County (1818 - Present)
Vermilion County (1826 - Present)
Wabash County (1824 - Present)
Warren County (1825 - Present)
Washington County (1818 - Present)
Wayne County (1819 - Present)
White County (1816 - Present)
Whiteside County (1836 - Present)
Will County (1836 - Present)
Williamson County (1839 - Present)
Winnebago County (1836 - Present)
Woodford County (1841 - Present)