So lets do a little experiment.
YOu will draw on a piece of paper a map of the USA as you think it looks (without looking at a real map) and draw on it a small circle to indicate where in this mystical Realm of the Old Lands your PC home village is likely located (include a village name), and the phrases "Here be Dragons" and "Forbidden Lands" in locations (One each) on the map with a dotted line around these two regions. You are not to look at anyone elses work until you have uploaded your own - no cheating.
SO scan/upload the map and use spoiler? on it to make it invisible. We do have spoiler right?
The idea is that one day we will do a real map of the USA and add all these villages and their map details.
Here is My Memory map of the USA...awesomly accurate. 
And behold the village of To'chan.
So why all this Memory map crap? Well Memory Mapping has at its core a formula that defines the amount of information any given community or population group has about another community or population group.
The level of information that the village of To'chan will know about any given other community is inversly proportional to the distance from the other community and proportional to that other community's population.
Information Recieved by location X about location Y = Population of Location Y / (isolation level of location X times square root of (Distance of location Y from location X))
i=p/k.sqrt(d)
Say you were doing a DC check on what anyone in To'chan knew of the village up the road. You would have to assume that the further that other community is the less your villagers would know of it. They would however know more about it if the population of that other village were greater.
If the village of Y were a population of fifty and a hundred miles away, it might be expected that the DC limit on what the population of To'chan might know of Village Y 1000 miles away with a population of 50 if both were connected by a major communication artery is very low. Low enough to not even be mentioned on a map or have it's name known. If it was a city of 10,000 then the population of To'chan will collectivly know a huge amount about the City of Y it simply because the city exports information about itself along the Primary artery of communication on which the village of To'chan sits.