In Mark Twain's The Adventures of Huckleberry Finn, Jim and Huck first begin their raft journey at the end of chapter 11 ("They're After Us!") and the beginning of chapter 12 ("Better Let Blame Well Alone"). They originally set out on the raft in order to avoid a search party trying to capture Jim and return him to slavery.
Huck and Jim travel on the raft for most of the rest of the book, although their travel is not constant. Rather, the novel is divided between episodic adventures that often take place on shore away from the raft. At the end of each of these adventures, Huck and Jim return to their raft to continue their travels and explore new regions. The raft and the Mississippi River maintain a constant presence that functions as the backbone of Twain's novel. As such, the role of the river in the novel mirrors the role of the real Mississippi River, which runs down the length of the United States and has historically served as an important driver of culture and economy.