Of old the Iron Mountains connected the Blue Mountains (Ered Luin) of the West to the Red Mountains (Orocarni) of the East, but in the wars between the Valar and Melkor the mountain range was distorted.
Melkor's great fortresses of Angband and Utumno were built in the mountains. North of the range lay the Forodwaith, a region of ever-lasting cold.
After the War of Wrath the Iron Mountains were broken and disappeared for a great part of their length. Remnants of the range in the Third Age included the Mountains of Angmar in northern Eriador, as well as the Ered Mithrin and the Iron Hills of northern Wilderland.
Ered Mithrin, the Grey mountains was in origin the last remnants of the wall of EredEngrin east of Hithaeglir and Forodwaith north of it was once Dor Daedeloth.
In the eastern end of Ered Mithrin the mountains divided into two spurs, a northern and a southern, between those two spurs the area were called Withered Heath.
As told was Forodwaith north of Ered Mithrin, south were from the west; the northern vales of Anduin, Mirkwood and furthest east Erebor.
Er errichtete zu seinem Schutz das Nebelgebirge und über Utumno die EredEngrin, die Eisenberge und dahinter lag Dor Daedeloth, die Gegenden ewiger Kälte.
In seinen Verliesen gab er den Maiar, welche ihm gefolgt waren, neue Gestalt.
Und in Utumno schuf er aus ihnen in langer Arbeit seine nützlichsten Sklaven, das Volk der Orks, die sich bald wie die Fliegen vermehrten.