I've been studying train routes for Sam's trip to St Louis in March of 1867. Explanatory notes at the Mark Twain Project and David Fears' Day By Day report that he departed New York on the New Jersey Central. It took two days to get to St Louis but the New Jersey Central would go no further than Easton, Pennsylvania. I've made an attempt at figuring out a route using the train route files from the University of Nebraska. They have kmz file for 1861 and 1870 - it's amazing how much growth in railroads there was between those dates - not to mention the difference with Sam's first journey to New York in 1853. Anyway, for any railroad historians out there, take a look at this and let me know what you think... https://twainsgeography.com/content/new-york-st-louis-march-1867