In his introduction to Undaunted Courage, Stephen E. Ambrose writes that he feels "privileged to have had the opportunity to spend so much time with Meriwether Lewis." With this expansive work, which he had wanted to write for twenty years, Ambrose takes the opportunity to unfold the Lewis and Clark drama. He makes it come alive, even for those readers who, unlike Ambrose, have never followed the Lewis and Clark trail.

By the publication of Undaunted Courage, several books had already appeared that chronicled the Lewis and Clark expedition. Still, this new work was immediately recognized as a valuable addition to historiography. Ambrose's thorough study provides telling details of the journey—drawing at all times on the extensive journals the company commanders wrote—and what its findings meant to early nineteenth-century America. His work is carefully placed in the context of the times, providing the reader the necessary comprehension of the morals and values of the period. Ambrose's work is unique for another reason. Throughout the book he injects his own enthusiasm for the incredible undertaking of traveling to a completely unknown land. The work also reflects his own admiration for the two men who were most important to it: Thomas Jefferson, the man who conceived it, and Meriwether Lewis, the man who carried it out.