A Brief History of
~ Thorin's Halls ~
in Ered Luin of Eriador
Now it came to pass that after the Sack of Erebor by the dragon Smaug in the year 2770 of the Third Age that Thrór son of Dáin, the exiled King of Durin's folk, led his kin into long and homeless wandering. But when twenty years had passed, Thrór, poor and desperate, left his people and went north with but a single companion for he wished to see the fabled city of his ancestors, Khazad-dûm; and there he was slain by Azog, an Orc-chieftain of Moria.
And Thráin son of Thrór sat for seven days without eating or sleeping, until he stood and said "This cannot be borne!"1, and he declared a war of vengeance against the Orcs of the Misty Mountains, and mustered all the Seven Houses of the Dwarves. And at the Battle of Azanulbizar in the year 2799 Thrór was avenged when Dáin Ironfoot removed the head of Azog and impaled it upon a spike.
Then Thráin with his son Thorin Oakenshield and the remains of his people returned to the hills of Dunland, and soon afterwards they removed and wandered in Eriador, until at last they made a home in exile in the east of the Ered Luin and there they established their Halls in the year 2802 of the Third Age. (Upon, it is said by some, the foundations of the ancient Dwarf city of Tumunzahar, which was ruined during in the War of Wrath in the First Age.)
There they prospered to some extent, but they worked mainly with iron and had little gold. Then after forty years Thráin, consumed with the lost riches of Erebor, travelled east with a small company of his kin and was lost under the eaves of Mirkwood, and Thorin was made ruler of Durin's folk. And under his leadership his people prospered; their trade increased as well as their numbers, for wandering Longbeards heard of Thorin's realm and came to him.
Thorin ruled in Ered Luin for nigh one hundred years, until he set out in the year 2941 to take back Erebor from Smaug the Great Worm, and reclaim his rightful place as King under the Mountain. But in the Battle of Five Armies, he was mortally wounded and his cousin Dáin Ironfoot of the Iron Hills became king of Durin's folk; and when tidings reached Durin's folk in the Ered Luin that Erebor was retaken, many of them removed to the Lonely Mountain, yet Thorin's Halls remained an important hub of trade in the region.
((N.B. The following is Lord of the Rings Online "lore" ONLY))
However, the rule of Thorin's Halls fell to the Dourhands clan, for Gormr Doursmith was appointed Steward by Thorin Oakenshield when he left for Erebor. Now the Dourhand dwarves hoped to restore their long-dead leader, Skorgrím, to life and therefore allied themselves with evil fell spirits of Old, just as Skorgrím himself did long ago; however in the year 3016 of the Third Age, King Dain sent a company of Longbeards to learn why the Master of Thorin’s Hall had ceased sending tribute to Erebor. And they, with the aid of the Sons of Elrond, uncovered the heinous plot to resurrect Skorgrim Dourhand, and together they fought to thwart that foul plan and reclaim Thorin's Halls. Following their victory, the Dourhands were expelled from the Halls, and Dwalin son of Fundin became the ruler there and so remains to this day.
This account was compiled by Angollon son of Ioriston
In the Scholar's Enclave of Duillond in Eriador
On the 42nd day of Rhîw T.A. 3018
At the behest of Todsi son of Bodsi of Erebor
1 J.R.R. Tolkien, The Lord of the Rings, Appendix A, "Durin's Folk"
A copy of this document may be found in the Istari Nalmë Archive of Lore within the Scholar's Enclave in Duillond.