Legality of Cannabis by U.S. Jurisdiction Illinois portalUnited States portalHistory portal This category is for topics specifically related to the year 1866 in the U.S. state of Illinois. 18611862186318641865186618671868186918701871 1810s1820s1830s1840s1850s1860s1870s1880s1890s1900s1910s Subcategories This category has the following 3 subcategories, out of 3 total. / 1866 disestablishments in Illinois (11 P) 1866 establishments in Illinois (20 P)E 1866 Illinois elections (1 P)