Jamieson, Fausset and Brown on 1 Chronicles 5:9

9. Eastward he inhabited unto the entering in of the wilderness from the river Euphrates--The settlement was on the east of Jordan, and the history of this tribe, which never took any part in the public affairs or movements of the nation, is comprised in "the multiplication of their cattle in the land of Gilead," in their wars with the Bedouin sons of Hagar, and in the simple labors of pastoral life. They had the right of pasture over an extensive mountain range--the great wilderness of Kedemoth (De 2:26) and the Euphrates being a security against their enemies.

1Ch 5:11-26. The Line of Gad.