I've completed adding probable railroad routes to my Twain-Cable tour
pages:  https://twainsgeography.com/content/twain-cable-tour

If you visit, click on "The Tour" option and this will open a page that
starts listing the tour dates.  Each of the tour date pages (most
anyway) have a Google map with a display of the route(s).  Most of the
routes I've mapped come from the files provided by the University of
Nebraska but are no more recent than 1870.  There was an explosion of
railroad lines between then and 1884-85.  I have attempted to improve
on the mapping by examining a number of map files provided by the
Library of Congress and topographic overlays available on Google Earth.

Railway lines failed, were absorbed by other companies, re-routed, etc.
And, there is very little if any mention of what lines Twain and Cable
took.  The tour date pages also have links to pages about the different
venues in which they appeared.  

I would very much appreciate leads to people knowlegable about these
topics.  This was a critical period in American history.  The railroads
were possibly the single most significant factor is how and why America
became what it is today.  The exploding population west of the
Mississippi and rapid industrialization occured because the railroads
provided the means.  Mark Twain was a witness to this.