Try Alan Lomax's "The Land Where the Blues Began", ISBN: 0-385-31285-7. Chapter 4, entitled Lonesome Whistles, is about the steamboats and railroads in the Delta. There are some lyrics for both and numerous interviews musicians and workers. There is a fairly recent release of Lomax's recordings that he made during these days; I'm not sure of the label (possibly Smithsonian-Folkways), but it may have some of these songs. I highly recommend the book.