The West-gate was made during the (undated) reign of King Durin III in Khazad-dûm. It was constructed with the aid of the Elves of Eregion, which places its making sometime between the founding of that realm in II 750 and its fall in II 1697.

There may very well have been an earlier West-gate, and indeed the fact that the Dwarves were able to make contact with Eregion strongly implies that such a gate did exist. That earlier gate would never have been known as 'Moria Gate', however. Indeed, neither the West-gate nor the East-gate would have been given that name until after the fall of Khazad-dûm. That took place in III 1981, when Thráin I fled from Durin's Bane and led his people away from their ancient home. Only after that time did Khazad-dûm become known as Moria.