With regards to the five places at the bottom, I have definite information that these places were founded after 1650, so in my world they don't exist. Having them on the list is still important, however, as the balance of their presence is subtracted from the total in order to determine the population for the remainder.
I have 10 places where I have a vague knowledge of when they were founded. Traditionally, Reykjavik was the first place in Iceland that was founded, and traditionally that year is 874. Who knows when it was actually founded or even if it was first; but for D&D purposes, I like using the myth over what may or may not be fact. A similar example occurs everywhere, so that is policy.
Of these 10, I have six that are described as appearing in the Landnamsold (linking the Icelandic page), which describes the first settlements in Iceland. Here is a pretty map:
|By Abraham Ortelius, cartographer, titled Islandia, circa 1590|
Most places have the same name today as they did long ago, with very few exceptions. That is also probably not quite true ~ but since I am working with English and not Icelandic (which must have variations), I don't care about too much nuance. Again, we're just looking for an approximation.
I've divided the place names into the four traditioning Farthings of Iceland, the old name for the provinces. The next step is to look up their latitude, longitude and elevation, so the places can be plotted on a map, and the map adjusted for the elevation of the hex that the place name will occupy. I'll be looking that information up on a glorious site called fallingrain.com.