National Geographic has a great new map of United States based on the distribution of common surnames which gives an idea of the country’s immigration waves.
I was particularly interested to learn that :
Many of these names came from Great Britain, reflecting the long head start the British had over many other settlers. The low diversity of names in parts of the British Isles also had an impact. Williams, for example, was a common name among Welsh immigrants—and is still among the top names in many American states.