The borders of Cardolan extended from the river Brandywine to the west, the river Hoarwell to the east and the river Gwathló (Greyflood) to the east and south. Its northern border was the Great East Road, but Cardolan also claimed the Arthedain-controlled Weather Hills, which contained the fortress of Weathertop and its valuable Palantír. For this reason the Weather Hills were claimed by all three kingdoms - Arthedain, Cardolan and Rhudaur. This territorial dispute continued until Rhudaur became a vassal of Angmar after the line of the Dúnedain kings failed there.
When the kingdom of Angmar arose in northern Eriador, Cardolan became the most important ally of Arthedain. It had to fight the combined armies of both Angmar and Rhudaur. It soon became apparent that Cardolan could not hold back the forces of Angmar and in its last years the people became entrenched in the hill region, Tyrn Gorthad (the Barrowdowns). This position became untenable after Angmar sent evil spirits to inhabit the downs (the Barrow-wights). Arthedain could provide little aid, as it was itself under attack. Around TA 1409Cardolan was destroyed, and its former inhabitants accepted the King of Arthedain as their lord. Arthedain managed to reconquer the land briefly, but few people wished to live there on account of the Barrow-wights, and so Cardolan was never re-populated.
After the final fall of Arnor, and the destruction of Angmar at the Battle of Fornost, Cardolan remained an unpopulated area until the reestablishment of the northern kingdom under KingAragorn II Elessar at the end of the Third Age. Until then, the region was largely unclaimed and known as Minhiriath.