The Night's Watch controls and directs the Wall. It extends from the mountain range of the Frozen Fangs, in the West, to the Bay of the Seals in the east, becoming the northern border of the Seven Kingdoms.
According to the legends, it was built after the period known as The Long Night by the mythical Brandon the Builder, around 8,000 years before the events that took place during the main story. The Wall was built to isolate forever the inhabitants of the Far North (especially the Others), who had invaded Westeros during that time, before being rejected by undisclosed forces (possibly the founders of the Guard, the children of the forest and others). Several mentions in the text suggest that the Wall was much smaller and lower at that time, and that it was reinforced by the Night's Watch over the centuries to its present size. However, at the time described in the books, the Night's Watch is weakened and is dedicated only to maintenance tasks. The greatest enemy of the Guard has been the Others, evil beings with supernatural powers.