MAP 7.2 American Indians in the Ohio River Valley, c. 1785–1795 In the early to mid-eighteenth century, despite periodic conflicts, Indian tribes in the Ohio River valley forged trade and diplomatic relations with various colonial powers. But once the United States established the Northwest Territory in 1785, conflicts between Indians and U.S. settlers and soldiers escalated dramatically. As tribes forged pan-Indian alliances, the United States constructed numerous forts in the region.