The major places, regions, and realms in the West Beleriand were the Arvernien, Dor-Cúarthol, Forest of Brethil, Havens of the Falas, Talath Dirnen (Guarded Plain), and Taur-en-Faroth. They were lands consisting mostly of hills, lowlands, and plains and bottomlands. There were some dense forests, as with the Forest of Brethil but much of it was scattered woodlands. There was also a moorland called the Moors of the Nibin-Noeg near the Forest of Brethil. The climate was mostly humid with mild winters and mild summers with some influence from the cold of the north around the gap between the Ered Wethrin and the Echoriath.
The region was populated and controlled by both the Sindar and the Ñoldor. Vast territory between the River Sirion, the northern mountains and the sea belonged to Finrod with the blessing of Thingol, Lord of Beleriand. Círdan was the Lord of the Havens of the Falas, the lands around the two rivers Brithon and Nenning next to the sea. The Forest of Brethil was settled in by the Men of the Haladin, who guarded it and Doriath from all enemies. The gap between the Ered Wethrin and the Echoriath was looked after by Orodreth, a relative of Finrod at the Fortress of Tol Sirion until it was conquered by Sauron. The land of Arvernien around the Mouths of Sirion was populated with both Sindar and Ñoldor, especially after the conquest of the realms of the north and the Beleriand by Morgoth in the mid and late centuries of the First Age.
The dominant language of the West Beleriand was Sindarin except in Nargothrond and the realm around Tol Sirion where Quenya was spoken. The Mannish language was used in Brethil by the men who lived there. Both Sindarin and Quenyan were probably used in Arvernien in the Havens of Sirion, as it was populated with many elves that were able to escape from the fallen realms of the Beleriand and the north.
All of the West Beleriand was destroyed after the War of Wrath and fell beneath the waves of the sea.
- The Silmarillion
- The Atlas of Middle-earth pgs. 11-16, 19 & 181-189
- The Complete Guide to Middle-earth