Mark Twain, whose real name is Samuel Clemens, is the narrator of Life on the Mississippi. The book’s narrative details the history of the Mississippi River and is intertwined with Twain’s personal narrative regarding his love of the river. As a child, Twain dreamed of becoming a steamboat pilot. He leaves home one day to fulfill this dream. Twain is adventurous, and becomes a trainee so he can learn how to pilot a steamboat. Along the way, Twain learns about river life and deals with various individuals, as well as with his own early bouts of cockiness and pride. Twain uses anecdotes and first-hand accounts to weave a story highlighting his growth on the Mississippi, his departure for war, and his eventual return to the Mississippi many years later.

The Mississippi River is arguably the most important character of the novel. Though it has no first-person voice, Twain details its history from its first glimpse by a white man, DeSoto, who called it a nondescript body of water, to its role in the growth of America and the South. The Mississippi is witness to many historic events in American history, and as Twain notes, has a more commanding place and presence in history than many other bodies of water worldwide that are better known.