[jmecklenborg]

Also, there is a railroad that runs directly between Cincinnati and St. Louis in more-or-less a straight line, and is about 40-50 miles shorter than a route that travels through Louisville or through Indianapolis. I'm sure that this line has plenty of capacity for passenger rail and could serve all of the small towns it travels through. There is no parallel interstate highway.

Unfortunately, I think there would be too much pressure to choose either the Louisville or Indianapolis route in order to pick up those population centers, but interstate highways parallel those railroads, and so there is direct competition for passengers.