I have discovered that CSX has broken the link I found in 2014 to a great map of the Chicago area railroads (http://209.118.csx.com/?fuseaction=home.maps). Unfortunately, I have been unable to find it again on their web site. Fortunately, because it is a big file, I had a local copy on my computers to save download time. So I have uploaded a copy to my web server:

B&OCT Map (PDF file)