I believe the main difference between "pioneers" and "mountain men" were primarily that pioneers often were composed of entire families searching for a new place to settle down, while mountain men were far more adventurous, preferring to keep on the move while they plied their trade (hunting, trapping, trading). Mountain men, as the name implies, usually travelled in mountainous regions, while pioneers often settled in westward lands that were not necessarily mountainous. The pioneer was generally searching for an unsettled land in which he could make his home and help to develop a new community, often with the basis of claiming new and previously unowned property. For example, Daniel Boone was one of the most famous pioneers: He led a group of people into Kentucky and created the settlement of Boonesborough. The film Jeremiah Johnson, on the other hand, was based on the real-life mountain man John "Liver-Eating" Johnson, who travelled into the Rocky Mountains to trap, hunt and seek gold while leading a solitary life in the wilds. Both pioneers and mountain men had to deal with hostile Native Americans, and both Boone and Johnson became renowned Indian fighters.