I was looking at United States Census data again recently and noticed some interesting ways of examining or analyzing it. You can download this data yourself direct from the Census Bureau here: Surnames occurring 100 or more times in the 2010 Census. The 2020 data won’t be out for quite some time. I sorted it by race (self-identified) and here are the surnames that had the highest percentage white and at least 10,000 individuals. All were 96.99% white or higher.
STOLTZFUS
BYLER
HERSHBERGER
TROYER
YODER
BURKHOLDER
HOSTETLER
GRABER
MAST
ROUSH

The dominance of German- and Jewish-sounding names on this list continued for several hundred more entries. Now for the blackest names by percentage, again with a cutoff of at least 10,000 individuals:
WASHINGTON
BANKS
JOSEPH
JACKSON
WILLIAMS
ROBINSON
COLEMAN
HARRIS
SIMS
DIXON

These percentages range roughly from 39% to 87% black. Presumably both these lists are formed largely by the history of slavery, with colonial slaveholders giving their slaves their own surnames, or possibly in some case, freed slaves taking the surname of a well-known white person. If I restricted the list only to the 1,000 most common names, some Irish names like O’Connell appeared in the whitest list, but most were still Germanic. Germans and European Jews tended to arrive in the U.S. in large numbers only after slavery ended and generally settled in free states or territories.

You can also use the data to find out how common your surname is and that of your mother’s and grandmother’s maiden names.