A mountain range stretching east to west to the north of Mirkwood and marking the northern boundary of Rhovanion. The sources of the Anduin and the Forest River are located there. At one time home to Durin’s Folk.

The Grey Mountains (Sindarin: Ered Mithrin) were rich in gold and other ores, and in TA 2210 Thrain I left Erebor with his folk and established extensive mines. The resultant wealth attracted the attention of dragons who began to spread and harass the dwarves. Eventually, in TA 2589 Dain I and his second son Fror were slain by a cold-drake.

The following year TA 2590 Dain’s heir Thror returned to Erebor with his people while Dain’s other son Gror took his folk to the Iron Hills. Subsequently the dragons multiplied and the old dwarf mines became infested with orcs.
Encyclopedia entry originally written by PotbellyHairyfoot