He describes, with great affection, the science of navigating the ever-changing Mississippi River in a section that was first published in 1876, entitled "Old Times on the Mississippi". Although Twain was actually 21 when he began his training, he uses artistic license to make himself seem somewhat younger, referring to himself as a "fledgling" and a "boy" who "ran away from home" to seek his fortune on the river, and playing up his own callowness and naïveté.
In the second half, Twain narrates his trip many years later on a steamboat from St. Louis to New Orleans. He describes the competition from railroads, and the new, large cities, and adds his observations on greed, gullibility, tragedy, and bad architecture. He also tells some stories that are most likely tall tales.
Simultaneously published in 1883 in the United States and Great Britain, the book is the first submitted to a publisher as a typewritten manuscript