Angtiria literally means "the land of the Ang", but the Ang have long since faded from the world after the Harad Migrations which brought new peoples to these regions of Eradain.
It is said in the Migrations of the Harad that two princes of the Harad traveled north from where the Harad first arrived in Eradain and encountered the Ang: "Prince Khor and Prince Sinann, closest of the two brothers, traveled together west and north and encountered the Ang. The Ang were a diminished people with empty villages and they welcomed the Harad into their lands and hearths. They helped both the princes and their people and taught them of the lands and the gods of Eradain. Prince Khor's people continued to the north taking with them Ang druids who would show them the plains of the north and the ways of nature. Prince Sinann and his people inter-married with the Ang, and before he died declared their people no longer Ang or Harad, but both: Angharad."
The legends further tell that the Harad Prince Sinann married a woman of the Ang and they had four daughters, Tiran, Raetha, Umirelle, and Runiver who are the founders of the four major Angharad Clan Houses. Tiran was a skilled Swordswoman and Sorceress who fought many battles and was a hero to the people. Raetha was the first Angharad Priestess of the Ang goddess Dana who founded The Circle and became its first Great Druid. Umirelle was a traveling Bard and Tinker who was a fearless explorer of the lands and author of songs still sung to this day. Runiver was a druid and a crafter who established the city of Tilith as a trade town and wrote many of the laws of the Angharad.
Using the Low-fantasy Population Generator with a rough estimate of Angtiria composed of twenty 50-mile hexes yields 43,000 square miles.