In addition to the fine information you guys provided here (much thanks!) I found another fun source:
In my stash of toy/model train books I found one titled "How to Build and Operate a Model Railroad" by Marshall McClintock. My copy is the first edition from 1955 and it is a wonderful guide for 1950's boys and their dads building their American Flyer enpires.
I'm enjoying reading and learning from it.
Did Mr. McClintock work for Gilbert American Flyer?