American Indians, that is Native Americans, are a very small minority now due to numerous reasons. For starters, many of them died because of the diseases that the colonists brought with them that the natives weren't immune to, like the measles. A large amount of them died when moving westwards as they were kicked out of their land, or in the wars for defending their land. What remains is those who accepted their life in reservations at the time.
The answer is Colonization
The study of historical writing
