The river is one of the most powerful motifs in Huckleberry Finn.

The majority of the plot takes place on the river or its banks. For Huck and Jim, the river represents freedom. On the raft, they are completely independent and determine their own courses of action. Jim looks forward to reaching the free states, and Huck is eager to escape his abusive, drunkard of a father and the "civilization" of Miss Watson. However, the towns along the river bank begin to exert influence upon them, and eventually Huck and Jim meet criminals, shipwrecks, dishonesty, and great danger. Finally, a fog forces them to miss the town of Cairo, at which point there were planning to head up the Ohio River, towards the free states, in a steamboat.

Originally, the river is a safe place for the two travelers, but it becomes increasingly dangerous as the realities of their runaway lives set in on Huck and Jim. Once reflective of absolute freedom, the river soon becomes only a short-term escape, and the novel concludes on the safety of dry land, where, ironically, Huck and Jim find their true freedom.