A Typology of Chicago Alleys

Primary Alley

Because of its reliance on the grid Chicago has been called one of the most right-angled cities in the world.  This may be true, but it doesn't mean that its development has been simple or monolithic.  Like any urban feature, the grid responds to the needs of those who use it.  Sometimes this is subtle, but there are some examples of grid flexibility in Rogers Park which are worth investigating.
 
The neighborhood of Rogers Park was incorporated as the Village of Rogers Park in 1878, but many of the earliest lots were subdivided in 1872 and 1873 and reflect a more suburban scale and character, with generous frontage and depth.  The area was annexed to Chicago in 1893 and the extension of city services and utilities led to steadily increasing development and density.  Many lots intended for purchase in the 1870s were subdivided to make them more attractive for the modest homes that came to the neighborhood in the 1900s and 1910s.  But the new lots still needed alley access, especially with the increasing popularity of the automobile.

Primary Alley Leading to Secondary Alley

Residential street right-of-ways are normally 66 feet wide in Chicago.  This reflected the length of the surveyor's chain, and established the modular dimensions of a typical residential block, which is 660 feet in length (10 chains) by 330 feet wide (5 chains).  Typical pavements are 32 to 34 feet from curb to curb, allowing for two lanes of parking and two lanes of traffic.  Streets with less than 30' of pavement were converted to one-way streets after 1967.  This was done following a particularly bad blizzard, which I'm grateful to have missed.

Grassy Private Alley

Typical alleys range from 16 to 20 feet.  Rear structures are set back 2 or 3 feet from the alley right-of-way, making the clearance a bit wider. Just like streets, alleys are owned and maintained by the city.

When a platted area is cut into smaller parcels a secondary alley will often become a part of that subdivision.  These are narrower, but are also public right-of-ways.  As fire-fighting equipment has become larger it's no longer acceptable to create these narrow alleys.

Private Alley Resembling Driveway

Private alleys are basically access roads carved out of the lots within the subdivision.  Several properties may own a portion of a private alley.  Because they're privately owned the city has no responsibility to maintain them.  Often these remain unpaved, or paved with gravel.  They can easily be mistaken for driveways.  Or if the owners decide they're no longer necessary they might disappear entirely, existing only on paper.

An easement might provide vehicle access like a driveway, or it might be intended to preserve access to light and air.  These are also the result of a private agreement recorded to the property.    I had no luck spotting the one easement contained in my study area.  But if anyone ever wants to be build a garage on top of it I'm sure it will again float to the surface.

The base maps for this post were developed from 80-acre maps on the City of Chicago's website and the 1937 edition of Sanborn Fire Insurance Maps accessed through the website of the Chicago Public Library.  Information about the public right-of-way reference CDOT's "Street and Site Plan Design Standards," also available on the City of Chicago's website.  All the sketches above are all taken from the study area.