Phillybdizzle at Reddit made this map based on the 1881 Census of England and Wales showing the most common surname in each province:
Any American will be familiar with the two most popular choices — Smith and Jones — but what's remarkable is how nearly perfectly the Smith/Jones divide lines up with the political boundary between England and Wales. In the United States, both Smith and Jones play as super-generic Anglo names. But in reality they seem to show pretty distinctively what part of the British Isles your male line hails from.