A Commentary, Critical, Practical, and Explanatory on the Old and New Testaments, by Robert Jamieson, A.R. Fausset and David Brown  at sacred-texts.com
jos 12:1THE TWO KINGS WHOSE COUNTRIES MOSES TOOK AND DISPOSED OF. (Jos 12:1-6)
Now these are the kings of the land, which the children of Israel smote, and possessed their land on the other side Jordan--This chapter contains a recapitulation of the conquests made in the promised land, with the additional mention of some places not formerly noted in the sacred history. The river Arnon on the south and mount Hermon on the north were the respective boundaries of the land acquired by the Israelites beyond Jordan (see Num 21:21-24; Deu 2:36; Deu 3:3-16 [and see on Deu 2:24]).
jos 12:7THE ONE AND THIRTY KINGS ON THE WEST SIDE OF JORDAN, WHICH JOSHUA SMOTE. (Jos. 12:7-24)
Baal-gad . . . even unto . . . Halak--(See on Jos 11:17). A list of thirty-one chief towns is here given; and, as the whole land contained a superficial extent of only fifteen miles in length by fifty in breadth, it is evident that these capital cities belonged to petty and insignificant kingdoms. With a few exceptions, they were not the scenes of any important events recorded in the sacred history, and therefore do not require a particular notice.