I recently found out, from the paper, about this website: World Names Profiler
It maps surnames (no matter how rare) in 26 countries by frequency, and down to region and county level.
For example, these are the results for the surname Asperger:
Nationally, by far the highest frequency of people named Asperger is in Hans Asperger's homeland of Austria - 13.29 per million. This would suggest around 110 people called Asperger in Austria. But the USA has a higher quantity, about 150 (0.49 per million). Germany has about 95 (1.14 per million).
In Austria the highest frequency is appropriately in Hans Asperger's native Vienna, and the regions directly to the north and east, bordering the Czech Republic and Slovakia.
In Germany the name appears most concentrated in what used to be East Germany, and in Berlin. In a 'Top Cities' section of the site, Berlin is given as the city 2nd in the world for quantity of Aspergers, behind another German town Friemar in the state of Thuringia.
The USA has the city 3rd in quantity of Aspergers - Chicago. But Michigan is the state with the highest frequency of the name. And within Michigan, Dearborn (Detroit metro) and Wyoming (Grand Rapids metro) appear to have the most. Asperger is also dotted across Ohio, Indiana, Illiniois and Missouri, so tends to be in the midwest. As well as Michigan, the name seems to be concentrated also in the St. Louis area and has also moved into California (Fresno, San Jose).