The pair are producing the 10-hour saga, based on Stephen Ambrose's book Undaunted Courage.
Norton explains, "We have friends who've been pointing out that there are some funny echoes, similarities between Lewis and Clark and us.
"I don't have any prejudice against it. At the moment, we're acting as good shepherds for the project. It's being written now."
The actor was so inspired by the novel that he decided to produce the project with Pitt for HBO.
Article Copyright World Entertainment News Network All Rights Reserved.