Arnon refers to the large river and surrounding valley region that flows in the Moab region east of the Dead Sea. This river formed the boundary between Moab and Amorite territory.
Num 21:13From there they set out and camped on the other side of the Arnon River, which flows out of the territory of the Amorites into the wilderness. The Arnon is the border of Moab, between Moab and the Amorites.Num 21:14That is why it says in the Book of the Wars of the Lord: “Waheb in Suphah and the valleys of the Arnon,Num 21:15and the slopes of the valleys that lead to the site of Ar and lie along the border of Moab.”
Judg 11:18Then they went through the wilderness and traveled around Edom and Moab. From the east of Moab they camped on the other side of the Arnon River, but they did not enter Moabite territory, because the Arnon was its border.
During the time of Jehu (King of Northern Israel), Aramaean King Hazael attacked as far as this place.
2 Kgs 10:33He cut off from Israel all the territory east of the Jordan, including all Gilead, from Aroer) by the Arnon Valley through Gilead) and Bashan, the land of the Gadites, Reubenites and Manassites.