Ered Luin
The Ered Luin, the Blue Mountains, are the great mountain range that forms the western boundary of Eriador and the eastern edge of Lindon, the last remnant of the Elvish realm in the West of Middle-earth. They are all that remains of the far vaster mountain chain that once divided the ancient land of Beleriand from Eriador, before Beleriand was broken and drowned in the Great War at the end of the First Age. In the Third Age, the range runs from the Gulf of Lune in the south northward for many leagues, and its western slopes look toward the Sea, while its eastern foothills border the lands of the Shire and the empty regions of Minhiriath.
Geography and the Elvish Haven
The Ered Luin are most famously associated with the Grey Havens (Mithlond), which lie at the mouth of the Gulf of Lune where the river Lune breaks through the mountains to the sea. Círdan the Shipwright dwells there, and from these havens the Elven-ships set sail for the Uttermost West, never to return. The Elves of the High Kindred still linger in Lindon at this time, and the three Elf-towers of the Tower Hills, visible from the western marches of the Shire, are said to be of immemorial age, though no Hobbit has ever climbed the tallest. The Ered Luin thus mark the boundary between the mortal lands of Middle-earth and the path to the Undying Realm, a frontier of departure and loss.
The Dwarf-Realm in Exile
After the destruction of their great mansions, the Dwarves of Durin's Folk found refuge in the Ered Luin. Following the War of the Dwarves and Orcs and the Battle of Azanulbizar, Thráin II and his son Thorin Oakenshield, with what remained of their following (including Balin and Glóin), wandered in Eriador until at last they made a home in exile in the east of the Ered Luin beyond the Lune. There they forged mostly iron, and though they prospered after a fashion and their numbers slowly increased, they had little gold or precious metal. It was in these mountains that Thorin Oakenshield lived as the Heir of Durin without hope, until his meeting with Gandalf at Bree led to the Quest of Erebor. The Dwarves of the Blue Mountains still have mines that are in use in the Third Age, and they are accustomed to pass east along the Great Road through the Shire on their way to the Misty Mountains and beyond.
The Eastern Border and the Shire
The Ered Luin form the western horizon of the Shire. The Hobbits of the Westfarthing say that one can see the Sea from the top of the tallest of the three Elf-towers on the Tower Hills, which are outliers of the range, though no Hobbit has ever climbed it. The ancient East-West Road runs through the Shire to its end at the Grey Havens, and Dwarves have always used it on their way to their mines in the Blue Mountains. The mountains thus serve as a constant, distant presence on the edge of the Shire's sheltered world, a reminder of the wider lands and the Sea beyond.
Narrative Significance
The Ered Luin function as a geographical and symbolic boundary in the narrative. They are the last landfall before the Sea for those who depart Middle-earth, and the first refuge for the exiled Dwarves. They are also the westernmost limit of the known world for the Hobbits of the Shire, a place of legend and departure. The range is mentioned in the Ring-verse as the home of the Elven-kings under the sky, and in the chapter titles of the book, the journey of the Fellowship begins in the Shire and moves east, leaving the Ered Luin behind as the last remnant of the Elder Days in the West.