Elves of Mirkwood

In Appendix B of the The Lord of the Rings, we're told that the early Second Age saw the migration of many of the Sindar from Lindon, and that some of these travellers founded forest-realms. We're also told explicitly that 'Thranduil, king in the north of Greenwood the Great [Mirkwood], was one of these.' However, there are accounts in Unfinished Tales of an earlier king of the Elves of Mirkwood, Thranduil's father Oropher, who was lost in the War of the Last Alliance. These accounts can be reconciled if we imagine Thranduil travelling east from Lindon with Oropher, helping to found a kingdom in Greenwood the Great, but not in fact becoming its king until the death of his father more than two thousand years later.

The Wood-elves were limited to the northeastern parts of the forest at the end of the Third Age, but this had not always been the case. Their realm was originally founded on and around the hill of Amon Lanc, in the south of the forest. The Elves moved northward at least four times in their history, at first to move away from the influence of Khazad-dûm and Lórien. In the Third Age, Sauron came to their old home of Amon Lanc and built Dol Guldur there, and Thranduil was forced to lead his people from their then home in the Mountains of Mirkwood to the far north of the wood, where he delved an underground fortress.