Undaunted Courage, published in 1996, was the first in-depth book about the Lewis and Clark expedition. By the early 1990s, when Ambrose first began to consider the project, no new works had appeared in about twenty-five years, even though a great deal of new research had emerged, including a revised edition of the letters and journals of the expedition members. As the reviewer for Publishers Weekly pointed out, the ‘‘journals of the expedition, most written by Clark, are one of the treasures of American history.’’ Ambrose decided to use this material to write an updated account of the Lewis and Clark expedition.

Undaunted Courage, as numerous critics agreed, earned its lofty title. An immediate critical and commercial success, Ambrose’s vivid retelling of this historic event captivated readers and reviewers alike. According to Dale L. Walker, writing in Wild West, Ambrose provided a ‘‘meticulous reconstruction’’ of the journey of the Corps of Discovery. Gilbert Taylor of Booklist called Ambrose a ‘‘stimulating tour guide,’’ one who ‘‘paces the mundane so well with the unusual that readers will be entranced.’’

While critics all greatly enjoyed Ambrose’s effort, they were not in complete agreement as to how much Undaunted Courage contributed to the body of work on the Lewis and Clark expedition. Malcolm Jones Jr. of Newsweek called it an ‘‘absorbing new history,’’ and Taylor praised the book for providing a ‘‘final glimpse at a pristine Eden before the crowd of trappers and settlers altered it forever.’’ Publishers Weekly, on the other hand, maintained that Ambrose did not add ‘‘a great deal to existing accounts’’ of the expedition. Jones, however, pointed out that Ambrose ‘‘uses his skill with detail and atmosphere to dust off an icon and put him back on the trail west.’’ Roger Miller, writing for Book Page Review, also commended the book for capturing the ‘‘flavor of life in the struggling nation, particularly on the frontier.’’ From Ambrose, for example, the contemporary reader learns of the partisan politics of the Jeffersonian era.

Another important element of the book was the insight it provided into Lewis’ early and post-expedition life, both often overlooked aspects. ‘‘Ironically, Hollywood—not to mention grade-school textbooks—tends to draw the curtain just when the story gets most interesting,’’ wrote Jones. ‘‘They say nothing, for example, about Lewis’s manic depression, his scandal-ridden political career or his eventual suicide at the age of 35.’’ Lewis’ relationships with other people were also deeply explored, such as his relationship with Jefferson, which Walker believed was ‘‘at the heart of Lewis’ life.’’ However, as Publishers Weekly pointed out, the friendship between Lewis and Clark also lies at the ‘‘center of this account.’’

Though the great respect that Ambrose holds for Lewis and his accomplishment is clear, Jones noted that Ambrose is a ‘‘remarkably balanced historian.’’ He is ‘‘neither a revisionist nor an apologist.’’ Ambrose also examines Lewis’ attitude toward American Indians, which may seem problematic to the modern reader. Wrote Jones, ‘‘Ambrose weighs shortcomings against positive attributes and ultimately presents us with a convincing hero.’’ David S. Dahl in The Region further heaped praise on Ambrose’s style: He ‘‘lets the explorers tell their own story as [he] quotes liberally from Lewis and Clark’s journals.’’

Ambrose wrote this book, in part hoping to inspire readers to explore the Lewis and Clark trail themselves. ‘‘The single thing I most wanted,’’ he told Peter Carlin of People Weekly, ‘‘was to enlarge the circle of the those of us who sit around the campfire talking about Lewis and Clark.’’ Ambrose’s efforts have paid off. Officials at state and national parks along the route say that in 1996 tourism was up as much as 15 percent over the previous years. Miller perhaps best summed up the perception of Undaunted Courage: ‘‘At its conclusion the expedition seemed a grand undertaking. Nearly two hundred years later, thanks to Ambrose, it still does.’’