Both, the Europeans and the American Indians had something that the others wanted. The Europeans had lots of manufactured goods that the American Indians were finding attractive, and the American Indians were providing furs which were very desired and highly appreciated among the Europeans.
The Europeans and the American Indians, by the means of the furs and the manufactured goods developed a nice trading relationship for some time. Unfortunately for the Indians, lot of them were trading furs for alcohol and became alcoholics, which totally ruined their lives.
