‘ All the cities of the Gershonites, according to their families, were thirteen cities with their suburbs.'
So the Gershonites acted as Levites in the northern territories, Asher, Naphtali, Issachar and Manasseh in Transjordan.
Related Commentaries of Joshua 21:33
Joshua 21:33
33 All the cities of the Gershonites according to their families were thirteen cities with their suburbs.