|Location||Between Beleriand and Eriador|
|Realms||Belegost and Nogrod and later realms of the Dwarves|
|Inhabitants||Dwarves (Broadbeams, Firebeards, and Longbeards)|
|Description||Great western mountain range|
|Other names||Ered Luin, Ered Lindon|
|Events||War of Wrath|
|References||Quest of Erebor, The Silmarillion|
In the Beginning
During the creation of Arda, the Blue Mountains were meant to line up directly with the Grey Mountains of the southlands, forming the western wall of Arda. They lay parallel to the Red Mountains and Yellow Mountains that formed the eastern wall. The Blue Mountains were originally connected with the Red Mountains by the Iron Mountains which stretched across the entire north. The symmetry of Arda was broken during the wars between the Valar and Melkor in the ages before the Years of the Lamps.
Before and During the First Age
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.
After the First Age
The Blue Mountains were ruined during the War of Wrath, and at the middle of the range the sea broke through. The River Lhûn now flowed through the mountains to the Gulf of Lhûn. On the west side of the Blue Mountains 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. Its most important city was the Grey Havens, from where departing Elves left Middle-earth for Valinor. Also located here were the two regions of Forlindon to the North, with it's chief port being Forlond. And Harlindon to the South, which Harlond was its chief port.
The Dwarven cities of Nogrod and Belegost were also ruined when the Blue Mountains were broken. Nogrod in the South was completely destroyed and Belegost in the North was ruined. Most of the Dwarves fled east to Khazad-dûm. Some however, remained in the Blue Mountains, working the mines that survived the destruction, and rebuilding their ancestrial halls. The Dwarves lived mainly in the Southern chain on the East side of the mountains.In the Third Age the Northern Blue Mountains would become the new home for many of Durin's folk who had become exiled from their halls in Erebor by Smaug the Dragon. After the War of the Dwarves and Orcs, King Thrain II made his kingdom in the Northern chain and his son Thorin Oakenshield, ruled after he went missing, which during his reign many of the wandering folk of Durin joined them and they became prosperous in a fashion. Until Erebor was retaken from the Dragon by Thorin and company. Then many of the Durin's folk relocated there.