Roads and expressways in Chicago
Chicago's streets were laid out in a grid that grew from the city's original townsite plan platted by James Thompson.
A scattering of diagonal streets, many of them originally Native American trails[citation needed], also cross the city.
Many additional diagonal streets were recommended in the Plan of Chicago, but only the extension of Ogden Avenue was ever constructed.
[1] As the city grew and annexed adjacent towns, problems arose with duplicate street names and a confusing numbering system based on the Chicago River.
This volume is available online in PDF format indexed by initial letter, Plan of Re-Numbering, City of Chicago, August 1909.
Downtown was defined as Lake Michigan on the east, Roosevelt Road (Twelfth Street) on the south, and the Chicago River on the north and west.
While all north–south streets within city limits are named, rather than numbered, smaller streets in some areas are named in groups all starting with the same letter; thus, when traveling westward on a Chicago street, starting just past Pulaski Road (4000 W), one will cross a mile-long stretch of streets which have names starting with the letter K (From east to west: Keystone (North Side)/Komensky (South Side), Karlov, Kedvale, Keeler, Kildare, Kolin, Kostner, Kenneth, Kilbourn, Kolmar, Kenton, Knox, Kilpatrick, Keating), giving rise to the expression "K-town".
These streets are found approximately in the 11th mile west of the Indiana state line, and so begin with the 11th letter of the alphabet.
The areas that might otherwise be the B through J groups are the older parts of the city where street names were already well established before this system was developed (although some small groups of streets seem to have been given names intended to conform to the system), and the Q group (8800 to 9600 W) would fall west of the city, as the only land in Chicago west of 8800 West is O'Hare International Airport, undeveloped forest preserve, and a small strip of land connecting O'Hare to the rest of the city and containing only Foster Avenue.
For example, the 54th/Cermak terminus of the Pink Line is located near the intersection of 54th Avenue and Cermak Road (22nd Street) in Cicero.
Suburbs that follow the Chicago numbering system include Berwyn, Bridgeview, Brookfield, Burbank, Channahon, Chicago Heights, Cicero, Crystal Lake, Elwood, Evergreen Park, Franklin Park, Justice, Lincolnwood, Matteson, Monee, Morris, Morton Grove, Niles, North Chicago, Oak Forest, Oak Lawn, Orland Park, Oswego, River Grove, Rosemont, Skokie, Westchester, unincorporated parts of Des Plaines, Glenview, and other parts of Cook County, Will, DuPage, Kendall, and Grundy Counties.
The six "collar" counties (DuPage, Kane, Kendall, Lake, McHenry, and Will) use State and Madison as a base line.
The aforementioned pattern also occurs in Waukegan, Illinois, with Washington Street being the baseline between north and south.
; all are numbered aside from Marquette Road, running at 6700 S, west from King Drive (400 E) to the city's western limit at Cicero Avenue (4800 W), near Midway International Airport.
[14] Only the designated streets in the townships of Lemont, Palos, Orland, Bremen, Lyons (south of the rivers) and Wheeling have the blue pentagon signs that are used to demarcate county roads.
