Why do you think it took the Manderlys to establish White Harbor at the mouth of the White Knife given its prime trading location? Do you see the North’s material existence or culture as particularly averse to founding permanent cities. Was it more of the fact that the area was (as detailed in WOIAF) highly contested between so many petty kings for so long? Historical contingency? Thanks for your reply.

Money, primarily. It’s not like the North didn’t use the mouth of the White Knife – the Wolf’s Den was fortified because that territory was useful to them. But the Manderlys had a depth of liquid capital that the less-fertile North simple didn’t have to hand, and because it was the only option, they invested all of it into a single location. This created the necessary labor demand for a proper city. 

But yes, the development of the Wolf’s Den was likely inhibited by the castle being the Vale’s focus of attack during the Worthless War and then suffering the effects of civil war and repeated change in management.