The recorded history of Westeros extends back over 12,000 years, according to tradition, though the accuracy of the legends and myths that recount much of this history is openly questioned by the maesters of the Citadel, amongst others.

The earliest written histories date back to about 6,000 years ago, when the Andal's first introduced writing to Westeros. The First Men had no writing system more advanced than runes for marking graves, thus all history before 6,000 years ago relies on oral tradition. Many of the events before 6,000 years ago in Westeros, during the Age of Heroes, are half-legendary, and some of the more fanciful tales of these times probably have little basis in reality. Still, all legends and oral histories may have some kernel of truth behind them. Written histories in Essos from the great civilizations of Valyria and Ghis also date back roughly five to six thousand years.

The Andal's originated in the land of Andalos, near modern Pentos, east across the Narrow Sea. Thus, the coming of the Andal's was bloodiest along the eastern coasts of Westeros, in the Vale, the Riverlands, and the Stormlands. Their overland migration waves only reached the western side of the continent generations later, and by that point they were clearly inevitable. Therefore, the rulers of the Westerland's and the Reach peacefully intermarried with chosen Andal groups, inviting them in and uniting with them to fight off the other Andal kingdoms in eastern Westeros.