Dorthonion was a forested highland region in the north of Beleriand. The hilly eastern section was called Ladros. Dorthonion was walled-in by the Echoriath ("Encircling Mountains") in the west and the Ered Gorgoroth ("Mountains of Terror") in the south.
In year 6 of the First Age King Thingol gave permission to the Noldor to settle the northern lands of Beleriand. North Dorthonion was ruled by the Elf-lords Angrod and Aegnor and Ladros was ruled by Finrod. After Finrod and his people removed to Nargothrond in the south, High King Fingolfin granted the land of Ladros to the House of Bëor as a fiefdom.