These lands and features include the Withered Heath, Iron Hills, Lonely Mountain (Erebor), Dale, and Laketown. The main bodies of water in the area are the rivers Celduin and Carnen (Redwater) which flowed further south into the Sea of Rhûn in the East.
The Northeast was made up of mountains, hills, and lowlands, which were made up of scrubs, stunted, trees, thickets, and scattered woodlands. The Northeast’s climate was normally cool due to its proximity to the polar north with severe winters and cool summers with cool and dry prevailing winds coming down from the north.
The inhabitants of this region were mostly Orcs, Dwarves, some Dragons, and Men. Due the nature of the peoples, underground living was preferable save for the Mannish peoples that didn’t live in the mountains or the hills. Languages spoken were Orcish dialects, Khuzdul, and Mannish languages especially Westron in later days.
These lands existed back in the earliest days of Middle-earth but what was later the Grey Mountains was in these days part of the long oppressive Iron Mountains that dominated the north. In these days, there were no known dwarf or orc colonies in the hills or in the mountains and dragons were not known to have lived in this area at this time, but tribes of Silvan elves and later Mannish tribes were known to be living in or near the Northeast.
After the War of Wrath when the Beleriand fell beneath the waves, the orcs and the remaining dragons fled into up into the mountains and hide and created hidden realms, and became an ever increasing threat. Starting at around TA 1980 when the Dwarves of Khazad-dûm were driven out of by the Balrog, dwarves began moving into the Grey Mountains and later into the Lonely Mountain and then into the Iron Hills. Men also began establishing themselves in Dale and Laketown and good relations between the dwarves and men prospered for many years. However, when the dragon Smaug heard of the happy prosperity of the two peoples and their treasures, he descended down upon the two realms and destroyed them. The dwarves were then forced to flee from the Lonely Mountain and the men moved south into Laketown.
After the Battle of Five Armies during the Quest of Erebor, the dwarves and the men regained both the Lonely Mountain and Dale and the North-east prospered for many years. The Northeast still thrived into Fourth Age despite attacks by the Easterlings, culminating in the Battle of Dale.
- The Atlas of Middle-earth pgs. 76-7 & 181-9