Why Chicago renamed and renumbered its streets in 1909.

In spite of the grid that existed from the time of James Thompson's survey of Chicago in 1830, navigating Chicago was not simple. 
The house and street numbering system was inconsistent and became more so as Chicago annexed adjacent towns. In 1880 the City Council took steps toward addressing the problem with an ordinance that adjusted house numbers south of Twelfth Street (Roosevelt Road) to match the numbered streets on the south side, but the measure neglected the central and northern portions of the city. The large-scale annexations of 1889 complicated matters further throughout the city.

In 1901, Edward Paul Brennan (1867-1942) proposed a solution, recommending State and Madison as the baseline for a city-wide street numbering system. 
Edward P. Brennan
In 1908, after years of debate, alterations, and improvements, the Chicago City Council adopted the plan, with implementation enforced beginning September 1, 1909. John P. Riley of the city's maps department was instrumental in hammering out the plan's final form.

The initial legislation exempted the Loop, but after its initial success, the Council amended the ordinance in 1910 to include that area, with a compliance date of April 1, 1911. In the following years, Brennan campaigned tirelessly for the elimination of duplicate street names and to ensure that the names of broken-link streets would remain the same throughout the city. Hundreds of street name changes resulted, Brennan suggesting many of the names adopted.
Change of Address Postcard.
The current method for adopting honorary street names reflects the determination of city leaders to preserve this rational system. On December 3, 1984, the City Council passed an Honorary Street Name Ordinance crafted by Charles O'Connor, head of the city's Bureau of Maps and Plats. Instead of changing a street's name to recognize a local hero, the city would create an honorary designation, posted on a special brown sign. The "real" address, however, for the purposes of mail delivery, police and fire departments, and the friend visiting from out of town, remained as part of the city's official grid-imposed street naming and numbering system. Brennan did not succeed in winning implementation for every aspect of his vision. For example, designations of Street, Avenue, and Road continued to be used randomly instead of being assigned to east-west, north-south, and diagonal streets respectivelybut his overall plan still makes life easier for every Chicago resident and visitor.
On Friday, August 23, 2013, a little before noon, a small ceremony was held to officially unveil the honorary street designation of the CORNER OF STATE AND MADISON STREETS as Edward Brennan Way.
Chicago Street Renaming Document of 1909
Chicago Street Renumbering Document of 1909 
Chicago Street Renumbering Document of 1911 for Loop Addresses.

Compiled by Neil Gale, Ph.D.