King of the West

King of the West was a title taken by Aragorn II Elessar on his accession to the throne of Gondor, signifying his kingship over all the Free Peoples of the West, from north to south.
In both the North- and South-kingdoms of the Dúnedain, there had been no king for many centuries. At the time of Aragorn's coronation, there had been no King of Gondor for 969 years and Arthedain, the last remnant of Arnor had been destroyed 1045 years prior. The last King to rule both realms jointly had been Aragorn's distant ancestor Isildur, though his Kingship was cut short at the Disaster of the Gladden Fields before he could truly take up the rule of his twin realms.
From that time, when the Third Age was just two years old, the West had had no uniting King. Aragorn's coronation was thus the beginning of the new Reunited Kingdom.