The “Mannaseh” here probably refers to the part of the tribe east of the Jordan, north of the Jabbok (Deuteronomy 3:13; (Deuteronomy 29:8), but it may include the part of the tribe west of the Jordan (Joshua 13:7). If both are in view, Jephthah’s tour was quite extensive.
29 Then the Spirit of the LORD was upon Jephthah, and he passed through Gilead and Manasseh and passed on to Mizpah of Gilead, and from Mizpah of Gilead he passed on to the Ammonites.