Kevin Costner's 'Horizon: An American Saga' is a multifaceted story that covers the expansion and settlement of the American West during the Civil War. Director, co-writer & star Costner, as well as other members of the film’s cast including Sienna Miller, Sam Worthington, Luke Wilson, Jamie Campbell Bower, Abbey Lee, Ella Hunt & Isabelle Fuhrman, spoke to The Hollywood Reporter all about working on the Western.