The Iron Hills were a range of hills in the northeast of the known parts of Middle-earth, in the middle part of both Rhovanion and Rhûn, east of the Lonely Mountain. It was home to a dwarf mining community, and in the Battle of Five Armies, Dáin II Ironfoot sent reinforcements to Thorin from here. The Iron Hills were the last remains of the Iron Mountains where Morgoth dwelt. They were founded by Grór son of Dáin I, after the Dwarves were exiled from the Grey Mountains. The Iron Hills were colonized by Dwarves around the year 2500 of the Third Age. The Longbeard Dwraves lived here.
The Dwarves of the Iron Hills were known for making a flexible iron armor from of course, the rich iron supply in the hills.