|This article's name may be incorrect.|
Northern Lordaeron is a name used to refer the unnamed closed zone wedged between the northwestern border of the Eastern Plaguelands, the northeastern border of the Western Plaguelands, and the southwestern border of the Ghostlands. Currently it is an inaccessible zone in-game that may be part of the fallen Kingdom of Lordaeron or of the Kingdom of Quel'Thalas. Also this is the place where the Thondroril River is born geographically.
As a curiosity, if the player swims around the shore from Tirisfal Glades to the edge of this zone, they will get a message stating that they have discovered Quel'Thalas. If they enter into the area, they will find some elven ruins, implying that high elves live or have lived there. Even though the Ghostlands and Eversong Woods were added in The Burning Crusade, this zone is still empty in-game.
This could be the land of the "northern vassals", whom Terenas's grandfather helped in their negotiations over their borders with the elves of Quel'Thalas.
It should be mentioned also that, although the high elves who did not become blood elves settled in many zones across Azeroth, a large number of high elves took refuge on some lands in the north of Lordaeron and adjacent to Quel'Thalas. This could be that location. In fact, Quel'Lithien Lodge is a town of high elves that is located adjacent to Northern Lordaeron in the Eastern Plaguelands and into the closed area, there are some elven ruins, indicating the presence of high elves in this zone.
There are some evidences to suggest that this unnamed area could actually be the mysterious Northeron mentioned in lore. In the first place early sketches had Northeron located in a southern Quel'Thalas region. Secondly Northeron could be a term shortened from Northern Lordaeron, though one must keep in mind the term Northern Lordaeron is based on conjecture and not an official term. And thirdly, both the orography, climate and vegetation of Northeron may be easily found an an area in the north of Lordaeron, in fact, the birth of a river as mighty as the Thondroril River logically should be located in a mountainous region, and Northeron is characterized by having mountainous regions inside his territory.
CataclysmThis section concerns content exclusive to Cataclysm.
With Cataclysm now out and flying mounts are available, Blizzard has blocked off all of the area from letting anyone fly in. However you can still see that it's mostly small hills and bumpy terrain.
Swimming from Tirisfal Glades is also blocked just a short distance past the northernmost stretch of accessible beach, making it impossible to swim to or from the Ghostlands along the western coastline. This may be due as much to the Burning Crusade barrier that blocks any travel north without passing through the instance-gate.
However, if one compares the dimensions of the land from the front gate of Stratholme in the Eastern Plaguelands, the front gate of Deatholme at the southern Ghostlands border, and the hills behind Hearthglen in the Western Plaguelands, it would seem that 'Northern Lordaeron' may be just Stratholme and its environs - or what it's become.