Friday, April 24, 2020

Why the North-South Chicago Streets Don't Align at North Avenue.

Chicagoans know that the north-south streets swerve abruptly on crossing North Avenue (1600N) from Kedzie Avenue (3200W) on the east to Oak Park Avenue (6800W) to the west, a distance of 4½ miles.
Chicago's streets are a grid pattern that is then overlaid on a spherical map of the Earth. All grids overlaid on spheres create an issue. They converge as the meridian's lines (north/south) approach the poles.

A surveyor laying out a grid has two choices. Either let the streets get closer together as they head towards the North Pole, meaning the building lots get smaller and thus would be sold for less money, or readjust the grid at intervals so that the lots and the profits don't shrink.

Chicago opted for the second choice. The abrupt readjustment, or so the story has it, is manifested most conspicuously at North Boulevard, which was at one time the northern boundary for the City of Chicago.
Looking North on Pulaski Road (Crawford Avenue) towards North Avenue, Chicago - 1947
Different people surveyed the townships to the north and south of North Avenue at different times.

The surveyors who laid out the city south of North Avenue were inaccurate. Harlem Avenue, the city's western border at that time, is 1/16 miles west of where it should be at Madison Street. That's 330 feet. If one had to hide a 330-foot mistake, they might parcel it out in small increments along the 5-mile width.

It's not like this is the only surveyor's error in Chicago. The whole city is 1.3° off true north. As a result, it doesn't square with the survey grid between the Wisconsin border and Central Street in Evanston, which was laid out independently.

Central and Golf Road is supposed to be parallel. However, if you follow the lines in a Street map or atlas, you'll find Central and Golf are 1½ miles apart in Hoffman Estates but only ½ mile apart in Evanston.

Who cared about such a slight difference at the time of the survey? They thought they were surveying farm property lines. They couldn't have imagined what the future would bring.

ADDITIONAL READING: Chicago's Eastside Begins at North Boulevard (1600N)

Compiled by Dr. Neil Gale, Ph.D.

1 comment:

  1. I read a fascinating book recently “Measuring America” by Linklater and find the whole process of metes and bounds so interesting. This is a great article. Surveying was a job done by good or sloppy workers, honest or dishonest workers.


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