Glenn and D both make good points and observations. I'd like to add that the house has been standing since the 20's. Check the inside for any cracks or shifted doorways or misaligned windows, tilting floors - all sure signs of structural movement. This may also be a sign of uneven settling, as it is an old house. If you can see the sill plates or basement ceiling joists, look for mosture stains or damage.
Also consider if you plan to remodel the kitchen and bath, as new owners often do, then you'll probably be opening that wall anyway.
My guess is it's likely what Glenn says, that it's because it's a north wall. But it's too big an investment to ignore even the slightes possiblitiy of a potentially serious problem. With these thoughts in mind, get an evaluation from an independent inspector (ie, not working for the bank or the realtor) and get some realistic answers to what is the cause of the moisture, and determine for yourself how serious a matter it is.
Let us know, okay? And welcome to the forum!