The original RR was built during the late unpleasantness. I believe it was washed out. King and Kenedy attempted to retard the rebuilding after the war to keep up the shipping rates on their steamers. Eventually it became "if you can't beat em, join em" and they back the initial section to Brownsville. Kelly's book, "River of Lost Dreams" suggests that their investment was largely to control the expansion of the RR so that it didn't put them out of business overnight. Both got out of the steamboat business in the early 1870's as the RR's began to have a heavy impact.