Charles Ellicott Commentary Numbers 32:34

"And the children of Gad built Dibon, and Ataroth, and Aroer," — Numbers 32:34 (ASV)

And the children of Gad built Dibon ... Better, repaired or fortified. Some of the cities mentioned in this and the following verses—as, e.g., Dibon and Heshbon—are also mentioned in Numbers 21:0 in connection with the conquest of the Amorite territory. It is not probable that new cities would have been built at this time, nor did the circumstances of the Israelites permit the delay that would have been involved in such an undertaking. It was at Dibon that the Moabite stone was discovered by Mr. Klein in 1868. For the geographical position and modern names of the towns mentioned in these verses, see Keil (on this passage). In the distribution of the towns by Joshua, some of the southernmost towns repaired or fortified by the Gadites appear to have fallen to the tribe of Reuben . Heshbon, on the other hand, appears to have fallen to the lot of the tribe of Gad and to have been assigned to the Levites (1 Chronicles 6:80–81).