I suspect a double error in some maps, while they place these two towns in Perea; much more, while they place them at so little a distance.
We do not deny, indeed, that the city Adam was in Perea; but Zaretan was not so. Of Adam is mention, Joshua 3:16; where discourse is had of the cutting-off, or cutting in two, the waters of Jordan, that they might afford a passage to Israel; The waters rose up upon a heap afar off in Adam. For the textual reading "In Adam," the marginal hath "From Adam." You may very fitly apply both readings.
Adam was the centre, where the waters parted: here was the station of the ark of the covenant, now ready to enter Jordan. Hence the Psalmist, The tabernacle which he had fixed in Adam, Psalm 78:60. Therefore, the textual reading "inAdam," holds well; because there was the centre of the cutting in two of the waters: but the marginal reading "from Adam," does moreover add light, because the gathering those waters together on a heap was far above it.
"R. Jochanan saith, Adam is a city, and Zaretan is a city, and they are distant from one another twelve miles." From Adam to Zaretan, were the waters dried up; from Zaretan and upwards, they stood on a heap. Adam was in Perea, over-against Jericho; Zaretan was in the land of Manasseh on this side Jordan. It is called Zarthanah, 1 Kings 4:12, and is defined to be near Beth-shean, which was the furthest bounds of the land of Manasseh northward. The brazen vessels of the Temple are said to be cast in the plain of Jordan, in the clay ground between Zaretan (on this side Jordan) and Succoth (beyond it), 1 Kings 7:46. Therefore, the words cited in Joshua, far off from Adam, which is beside Zaretan, are so to be understood, as not so much to denote the nearness of Adam and Zaretan, as to intimate that the heaping up of the waters was by Zaretan. They are to be rendered in this sense, "And the waters that came down from above stood together; they rose up into one heap, in a very long distance from the city Adam," namely, to that distance, which is by Zaretan.
Adam and Zaretan, on this and the other side, were both something removed from Jordan: but they are named in that story, because there the discourse is of the time, when Jordan contained not itself within its own channel, but had overflown its banks.