The great cities of Gondor were established in the late Second Age, and the purpose of the Stonewain Valley was to carry stone for their building, so it was clearly made very early in Gondor's history. This would date it to II 3320 or shortly afterward. By the end of the Third Age it had been generally forgotten, having fallen out of use many generations beforehand. It was not forgotten by the Drúedain, however, and thus the Rohirrim were able to ride along it to the defence of Minas Tirith on 14 March III 3019.

Actually, the valley seems to have started some distance eastward from the peak of Nardol, but it could still be said to begin on the mountain's wide eastward slopes (hence its description as running 'from Nardol to Dîn' in The Return of the King V 5, The Ride of the Rohirrim). This course took it southward of the Eilenach Beacon and the Drúadan Forest, emerging somewhat southward of Amon Dîn.

All our references, both text and maps, agree on this general geography, with a single awkward exception. Earlier in the chapter referenced above, Ghân-buri-Ghân twice describes the Stonewain Valley as starting near Min-Rimmon. For instance, he describes it as being '...there behind Rimmon' (ibid). This is odd, as Ghân was speaking in the Drúadan Forest and describing a mountain some eighty miles to the west. In early drafts the name 'Min-Rimmon' was used for the Beacon-hill later called 'Eilenach', and the retention of 'Rimmon' here seems to be an editorial oversight. That is, when references to 'Min-Rimmon' were changed to 'Eilenach', this paragraph was apparently overlooked.

It is, however, conceivable that Tolkien really did intend that the valley ran on westward as far as distant Min-Rimmon. On balance, this seems unlikely, but there is sufficient room for doubt about the intended meaning that the original text is retained even in the latest editions of The Lord of the Rings.