Mike G wrote:

Not surprisingly, it's very non-PC-- probably why it didn't wind up in the recent Maps exhibit at the Field Museum

The map by sociologist Frederick Thrasher was in a book published by no less than The University of Chicago Press. I know the curators of the map exhibit at the Field Museum and I'm sure that when making selections the fact the Gangland map was non-PC never crossed their minds. Their objective was to show the great variety of maps produced over thousands of years. Given limited space many fascinating items had to be left out.

Politically incorrect was not unusual in that era. An even more colorful gang map from 1931 was by Bruce-Roberts, Inc. The title is "A Map of Chicago's gangland from authentic sources: designed to inculcate the most important principles of piety and virtue in young persons, and graphically portray the evils and sin of large cities." It's illustrated and discussed in "Chicago In Maps" by Robert A. Holland, pp. 164-167 (currently in print). There are also a couple of images on-line.