Angmar (Sindarin: 'Iron-home') (Pronounced: Ong-Mar) was founded in T.A. 1300 in the far north of the Misty Mountains by the evil Lord of the Ringwraiths, who became known as the "Witch-king of Angmar". Since the Witch-king was a servant of the dark Lord Sauron, it is presumed that Angmar's wars against the successor kingdoms of Arnor were done at Sauron's bidding to destroy an important ally of Gondor.
The capital of Angmar was Carn Dûm where a race of evil men lived.
Soon after Angmar was founded it waged war against the divided Dúnedain realms of Arthedain, Cardolan and Rhudaur. The Witch-king conquered Rhudaur, the weakest of Arnor's successor kingdoms, and replaced its Dúnedain king with one of the native Hillmen, a wild tribe of men possibly descended from the "accursed" kin of Ulfang.
Now under the Witch-king's control, Rhudaur in 1356 T.A. invaded Arthedain and in the attack, Arthedain King Argeleb I was slain. However, with the aid of the armies of Cardolan, Arthedain managed to maintain a line of defence along the Weather Hills.
In 1409 T.A. Angmar attacked Cardolan, destroying the kingdom. At this time, the Rhudaur disappeared, leaving Arthedain as the last remaining Dúnedain kingdom in Arnor. Arthedain, bereft of allies, struggled on for another 500 years. The end came in 1974 T.A., when Angmar amassed its forces and launched a final assault on Arthedain. Angmar took the Arthedain capital Fornost, thereby destroying the last kingdom of the Dúnedain in the North.
A year later, Prince Eärnur of Gondor arrived to aid Arthedain, but he was too late. His army, along with the remaining Dúnedain, the Elves of Lindon, a company of hobbit archers, and elven forces set out from Rivendell led by Glorfindel utterly defeated the forces of Angmar in the Battle of Fornost, but the Witch-king was not slain. He escaped and fled to Mordor, and his kingdom of Angmar dissipated. It was after this battle that Glorfindel made the famous prophecy that the Witch-king would be killed by no man. It should be noted that the Witch-king had achieved his master's wishes : the power of the Dúnedain of the north was destroyed forever.
Following the victory, Angmar's forces west of the Misty Mountains were completely shattered and it ceased to exist. Meanwhile, the parts of it extending on the east of the Misty Mountains were wiped out by the ancestors of the Rohirrim.
In The Lord of the Rings Online: Shadows of Angmar, the remains of Angmar consist of a mountainous, barren wasteland populated by hillmen and a large army of the Witch-king amassed to conquer Eriador. At the northern edge of Angmar are the ruins of Carn Dum, which have been partially rebuilt and populated with the Witch-king´s forces. Players can venture into Angmar to perform quests and fight the creatures there, as well as entering several instanced dungeons.