| Illinois County Formation years | ||||||||||||||
| 1790 | 1795 | 1796 | 1800 | 1801 | 1803 | 1809 | 1812 | 1813 | 1814 | 1816 | 1817 | 1818 | 1819 | 1821 |
| 1822 | 1823 | 1824 | 1825 | 1826 | 1827 | 1829 | 1830 | 1831 | 1833 | 1834 | 1835 | 1836 | 1837 | 1839 |
| 1840 | 1841 | 1843 | 1845 | 1847 | 1848 | 1851 | 1852 | 1853 | 1854 | 1855 | 1859 | 1869 | ||
| Illinois Census Year with Modern Map overlayed: | ||||||||||||||
| 1810 | 1818 | 1820 | 1830 | 1840 | 1850 | 1860 | 1870-1930 | |||||||
| Illinois Map Abbreviations | ||||
|---|---|---|---|---|
| unorg. = unorganized g. = gained w. = with fr. = from atmt. = attachment exch = exchanged nca.= non county area ch. = changed Ad - Adams Al - Alexander Bon - Bond Boo - Boone Br - Brown Bu - Bureau Cal - Calhoun Car - Carroll Cas - Cass Cha - Champaign Chr - Christian Cli - Clinton Clk - Clark |
Cly - Clay Col - Coles Coo - Cook Cr - Crawford Cu - Cumberland DK - De Kalb Do - Douglas DW - De Witt DP - DuPage Edg - Edgar Edw - Edwards Ef - Effingham Fa - Fayette Fo - Ford Fr - Franklin Fu - Fulton Ga - Gallatin Gr - Grundy Gre - Greene Ham - Hamilton Han - Hancock Har - Hardin Hry - Henry |
Hsn - Henderson Ir - Iroquois Jac - Jackson Jas - Jasper JD - Jo Daviess Jef - Jefferson Jer - Jersey Jo - Johnson Ke - Kendall Kke - Kankakee Kn - Knox Kne - Kane Lak - Lake Law - Lawrence Lee - Lee Li - Livingston Lo - Logan LS - La Salle Mad - Madison McD - McDonough McH - McHenry McL - McLean |
Mcn - Macon Men - Menard Mer - Mercer Mor - Morgan Mou - Moultrie Mpn - Macoupin Mrn - Marion Mro - Monroe Msc - Massac Msl - Marshall Msn - Mason Mty - Montgomery Og - Ogle Peo - Peoria Per - Perry Pia - Piatt Pik - Pike Po - Pope Pul - Pulaski Put - Putnam Ra - Randolph Ri - Richland |
RI - Rock Island Sal - Saline San - Sangamon SC - St. Clair Sch - Schuyler Sco - Scott Sh - Shelby Sta - Stark Ste - Stephenson Ta - Tazewell Un - Union Ve - Vermilion Wab - Wabash War - Warren Was - Washington Way - Wayne Wil - Will Win - Winnebago Wo - Woodford Wsd - Whiteside Wsn - Williamson Wte - White |