Who is Jack Mercy from Montana Sky and what is their importance?

Jack Mercy was the father of Tess, Lily and Willa Mercy. He was a hard and unforgiving man. Though the novel opens with the funeral of Jack Mercy, it is clear that in death Jack is just as strong a force as he was in life. Unwilling to give an inch to anyone, Jack Mercy lived his life his way, not caring who he hurt or what anyone thought.