The Clare sisters come to their own conclusion in the novel, focusing the last third on Clark and creating the story of what he does after Lewis dies to solve the mystery of what happened to his friend.
Following the Lewis and Clark trail from Fort Benton, Montana to the Pacific Ocean was important to the success of the novel.
"To really understand the achievement of the Lewis and Clark expedition," Mary Clare said, "you have to go and see how remote it was and in some ways still is. It was a spectacularly amazing feat of planning and courage to lead men over so many obstacles."
Clare said traveling the route Lewis took during the last days of his life to the place he died was especially moving.
"We drove all the way up the Natchez Trace until we got to the spot where Lewis died and is buried," she said. "It is such a lonely place but somehow it felt fitting that he should be there in that bit of wilderness in Tennessee."
The novel has earned a lot of attention and praise since it was published in September 2006. It won a silver medal at the Independent Publisher Book Awards and was named a finalist for the Foreword Magazine Book of the Year Award. It also received a "highly recommended" rating from Library Journal and won praise from the Western Writers of America, who called it "superb."
Clare believes the partnership and friendship that are central to the story are what draws people in and the extraordinary journey Lewis and Clark took is impossible to ignore.
"The heart of the story is Lewis and Clark's friendship and what it was about it that made their partnership work. It is about friendship and trust," Mary Clare said. "They took 30 men on an 8,000-mile journey and there was no conflict. They were complete partners.
The story keeps you wondering what Clark will do when he finds out what happened to Lewis."
Prior to working at the university, Clare was a columnist for the Austin Business Journal. Liz Clare writes and designs historical exhibits for the Texas State Library and Archives.
"To the Ends of the Earth: The Last Journey of Lewis & Clark" is available at Book People and Amazon.com.
The sisters are now working on "Beneath Our Native Sky," a prequel to their first novel. The book will be about Lewis and Clark as young men meeting for the first time in the army.
