Geographers at University College London used phone directories to find the predominant surnames in each state. Software then identified the probable provenances of the 181 names that emerged. (Zoom in, here
Many of these names came from Great Britain, reflecting the long head start the British had over many other settlers. Also, slaves often took their owners' names, so about one in five Americans now named Smith are African American.
Do you spot your last name on the map
National Geographic website