Roads and expressways in Chicago

Roads and expressways in Chicago summarizes the main thoroughfares and the numbering system used in Chicago and its surrounding suburbs.

Street layout

Chicago's streets were laid out in a grid that grew from the city's original townsite plan. Streets following the Public Land Survey System section lines later became arterial streets in outlying sections. As new additions to the city were platted, city ordinance required them to be laid out with eight streets to the mile in one direction and 16 in the other direction. A scattering of diagonal streets, many of them originally Indian trails, 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. In the 1950s and 1960s, a network of superhighways was built radiating from the city center.

As the city grew and annexed adjacent towns, problems arose with duplicate street names and a confusing numbering system based on the Chicago River. On June 22, 1908, the city council adopted a system proposed by Edward P. Brennan; amended June 21, 1909. The changes were effective September 1, 1909 for most of the city.Addresses in Chicago and some suburbs are numbered outward from baselines at State Street, which runs north and south, and Madison Street, which runs east and west.