Blue Mountains

Early history

In the early days of Arda after the fall of the Two Lamps, the Blue Mountains were formed as the Valar widened the Great Sea and thrust Middle-earth eastward to protect Valinor. The Blue Mountains lined up with the Grey Mountains of the southlands, forming the western wall of Arda. These two ranges lay parallel to the Red Mountains in the northeast and Yellow Mountains in the southeast that formed the eastern wall. At their northern end, a narrow gap separated the Blue Mountains from the Iron Mountains, which stretched across the entire north of Middle-earth.

Sometime during the Years of the Trees two Dwarven Fathers awoke under Mount Dolmed and founded the two westernmost houses of the Dwarves (the Firebeards and Broadbeams). They subsequently built two great city-states, Nogrod and Belegost.

In the First Age, the Blue Mountains were an unbroken line separating Eriador from Beleriand. Seven rivers flowed from its western side, and the land these rivers flowed through was known as Ossiriand. Later, when the Green-elves settled there, the land was called Lindon, and the mountains sometimes referred to as the Ered Lindon. Wandering Elves would also hunt in the Blue Mountains.

The Blue Mountains were ruined during the War of Wrath at the end of the First Age, and in the south central end of the range the sea broke through. The River Lhûn now flowed through the mountains to the Gulf of Lune. On the western side a small section of Lindon remained, and here the retreating Elves built the kingdom of Lindon, ruled by Ereinion Gil-galad, last High King of the Noldor.

The Dwarven cities of Nogrod and Belegost were also ruined when the mountains were broken, causing most of the Dwarves to migrate east to Khazad-dûm, leaving a remnant behind. However, there remained some Dwarves on the eastern side of the Blue Mountains in days afterwards.

Third Age

By the Third Age, Dwarves dwelt in the east side of the Blue Mountains, especially in the parts south of the Gulf of Lhun.

In T.A. 1974, fleeing the fall of Fornost Erain, Arvedui briefly hid in old dwarven mines in the far north of the Blue Mountains.

It also became the new home for many of Durin's Folk who were exiled from their halls in Erebor by Smaug the Dragon who had driven them out. After the War of the Dwarves and Orcs, King Thráin II established his throne in the Southern range beyond the Shire (T.A. 2802) and later his son Thorin ruled after he went missing. During Thorin's reign, many of the wandering Longbeards joined him in his halls and they became prosperous in a fashion. However, Erebor was retaken from Smaug by Thorin and company in T.A. 2941, and it can be assumed most if not all of Durin's folk relocated there.

However the dwarf-mines remained active even by the Fourth Age.