We don't have a specific date for the founding of the Rangers of Ithilien. The estimated date of III 2901 shown here refers to a time when Uruks emerged out of Mordor and forced most of the remaining people of Ithilien to flee the land. The emergence of the Uruks was answered in the same year by the establishment of Henneth Annûn, the secret refuge of the Rangers, which implies that the Rangers themselves also came into existence in this year.

Henneth Annûn lay near the northern edge of Ithilien, but in such an extensive region it seems hardly plausible that the Rangers didn't maintain other hidden refuges in other places. If so, we know nothing of them; Henneth Annûn is the only such place named or described in any detail.