Follow Up to the Blue Mountains Question - Gundabad

[Kuruharan]

I was going off information from Appendix A.

I think the contradiction is more apparent than real.

Gror, Dain's third son, went away with many followers to the Iron Hills
-Appendix A

That says that Gror went there, it doesn't say he founded the settlement there.

That begs the question though, that if the Dwarves had been established in the Iron Hills for so long, why was it only in the Third Age that they settled Erebor?

That is another very good question. My speculation on it is that Erebor was out of the dwarves usual route before the fall of Khazad-dum and fell under the same category as the Grey Mountains which were "little explored."

Of course, this brings us to a real contradiction where in Dwarves and Men it is said that the Grey Mountains were part of the Longbeard's empire during their height in the Second Age...and then after the fall of Khazad-dum they were suddenly "little explored."

Part of what I think may be going on here is another aspect of Tolkien's struggle to reconcile the events in The Hobbit with the rest of the broader world and this is a bit that didn't get ironed out very well.