The westernmost region of the lost realm of Arnor. Bounded upon the north by Forochel and the west by the Lune; upon the east by the Weather Hills and the south by the Baranduin. Arthedain nominally included the Shire.
After the death of Eärendur, King of Arnor, his three sons fought for the crown. Finally they divided the Kingdom in three so that each of them could rule their own realm. The first king of Arthedain was Amlaith, who ruled from 861-946. He was followed by Beleg (946-1029). After Beleg came Mallor (1029-1110), Celepharn (1110-1191), Celebrindol (1191-1272, Malvegil (1272-1349), Argeleb I (1349-1356), Arveleg I (1356-1409), Araphor (1409-1589), Argeleb II (1589-1670), Arvegil (1670-1743), Arveleg II (1743-1813), Araval (1813-1891), Araphant (1891-1964) and Arvedui (1964-1974).
Amlaith was the rightful heir to Eärendur, and the rulers of Arthedain were direct descendants of the Kings of Arnor.
861: Death of Eärendur. Division of Arnor. Amlaith becomes first King of Arthedain.
1356: King Argeleb I slain in battle with the Rhudaur.
Fourteenth century: The greatest of the Black Riders establish the kingdom of Angmar. Build a great citadel in Carn Dûm.
1409: King Arveleg I slain in an invasion from the Witch-king of Angmar. Tower of AmonSûl is destroyed.
1601: King Argeleb II grants land beyond the Baranduin to Periannath coming from Bree. Thus, the Shire is founded.
1940: Renewed communications and alliance between Gondor and Arthedain. Arvedui weds Fìriel, daughter of Ondoher, King of Gondor.
1944: Ondoher and his sons are slain in battle with Wainriders. Arvedui claims the crown of Gondor.
1945: Crown of Gondor given to Earnil II, by the Council of Gondor.
1974: Arthedain overrun by the Witch-king. Fornost taken. Arvedui Last-king escapes to the north.
1975: Arvedui drowned in the Bay of Forochel. The Witch-king defeated at the Battle of Fornost. He vanishes from the north.
1976: Aranarth takes the title of Chieftain of the Dunedain. The heirlooms of Arnor are given into the keeping of Elrond.
With the fall of Arthedain, Sauron secured a major victory in his war against the Dúnedain: the destruction (that is, as far as he was aware) of the northern line of Kings. Within a century, he would secure a second victory: the end of the line of Kings in Gondor.