First Men

The First Men are the original human inhabitants of Westeros. They ruled the continent for millennia before the Andals invaded from the eastern continent of Essos. The Andals overran most of southern Westeros, but failed to take the North. Whilst the blood of the First Men and the Andals has intermingled over thousands of years of dynastic marriages, the inhabitants of the North continue to claim that they have the greatest amount of First Men blood in their veins.

In the books
In the Song of Ice and Fire novels, the First Men invaded Westeros some twelve thousand years before the events of the series, crossing via a land-bridge from Essos in the vicinity of modern Dorne. They were resisted by the Children of the Forest, a semi-mythical dimunitive race who ruled Westeros alone at this time. The Children, using magic, destroyed the land-bridge (forming the modern peninsular of Dorne and the shattered islands known as the Stepstones beyond) but were pushed back over the course of many years of warfare. Eventually, the First Men and the Children forged the Pact, signed on the Isle of Faces at the centre of the vast lake known as Gods Eye. The First Men began to forge numerous kingdoms across the continent.

The two races coexisted peacefully for four thousand years before both came under attack from the Others, a mysterious race of ice and cold from the uttermost north. In the War for the Dawn, the First Men and the Children unified to throw back the invasion, raising the Wall to defend against their return. The greatest leader of the First Men in this war is held to be Brandon Stark, Bran the Builder, the first King in the North who built both the Wall and Winterfell. The peoples of the North unified under the leadership of House Stark at this time. After this war the Children began dwindling in numbers, with the last of them disappearing around the time that the Andals invaded Westeros (two millennia after the War for the Dawn, according to tradition).

The Andals overran and conquered all of Westeros over a period of more than a thousand years. Their attempts to conquer the North were defeated at every turn, and eventually the Andals and First Men made peace. Ties of dynastic marriage were made between the North and the southron kingdoms, so that the blood of both peoples mingled together, a process that has continued under the rule of the Targaryen kings.