We have two lines of evidence for dating the settlement of Dorthonion, and the first comes from Quenta Silmarillion 17, Of the Coming of Men into the West, where we're told that 'The Edain did not long dwell content in Estolad...' and that '....after some fifty years many thousands had entered the lands of the Kings.' These lands included Dorthonion (and indeed the coming of Men to Dorthonion is specifically mentioned in the same passage) which implies a date of about I 360 or shortly thereafter.

The second line of evidence comes the fact that we know the first lord of the Men of Dorthonion was Boromir, who was a great-grandson of Bëor the Old, and this raises something of a problem. In the year I 360, Boromir's father Boron was still alive, and would remain so for at least another four decades, which raises the question: why did Boromir become the first lord of the Men of Dorthonion, and not his father Boron?

There are at least two possible answers to this. Perhaps the most obvious solution would be to assume a much later date for the settlement of Dorthonion - in I 410, say, when Boron was dead and Boromir would have inherited the leadership of his people (the latest possible date on this reading would be I 432, the date of Boromir's own death). This does not, however, sit easily with the clear statement in the Silmarillion that this people 'did not long dwell' in Estolad, since it would require 'not long' to be a period of about forty years.

Perhaps a more plausible explanation would be that Boron gave up the leadership of his people to his son long before his death. Many of the older Edain remained behind in Estolad (Boron's contemporary Marach was known to have done just this), so perhaps Boromir led his people to Dorthonion while his father remained behind. Alternatively, it's possible that Boron entered the direct service of the Eldar as his grandfather Bëor had done, leaving Boromir to inherit his lordship. Lacking any detailed biography of Boron, it's impossible to be sure on these points, but a scenario like this fits the earlier dating of about I 360 much more easily, and reconciles the limited lines of evidence available.

We don't know of any specific settlements in Ladros, at least until the Dark Lord's forces overran Dorthonion after the Dagor Bragollach. After that time Barahir and his outlaws camped at Tarn Aeluin in the highlands between Ladros and Dorthonion proper, but that tarn was not a settlement beforehand (indeed we're told that there were '...wild heaths about it, and all that land was pathless and untamed...' in Quenta Silmarillion 19, Of Beren and Lúthien). Our only real glimpse of the former settlements of the Men of Dorthonion is of the house of Gorlim, one of Barahir's companions, which was a lonely homestead surrounded by fields and woods rather than part of a village or town.