Jefferson Township, Cook County, Illinois

Jefferson Township is a former civil township in Cook County, Illinois, United States that existed as a separate municipality from 1850 until 1889 when it was annexed into the city of Chicago. Its borders were Devon Avenue on the north, Harlem Avenue on the west, Western Avenue to the east, and North Avenue to the south. This region comprised most of what is now known as the Chicago's Northwest Side including the entirety of the following community areas: Jefferson Park, North Park, Albany Park, Irving Park, Avondale, Hermosa, Belmont-Cragin, Montclare, Portage Park, as well as parts of Forest Glen, West Ridge, Lincoln Square, North Center, Logan Square, West Town, Humboldt Park, Austin, Dunning, the suburb of Norridge, the suburb of Harwood Heights, and Norwood Park.

During its brief history it developed from unpopulated wildlife to a largely rural community with a number of suburban villages. However, due to infrastructure limitations, legislative incentives and the lure of better municipal services it, along with numerous adjoining townships, agreed to be annexed into the city of Chicago, creating the largest city in the United States at that time.