For a small area with about one million people Wales seems to be quite prolific. Here are the top dozen last names in the US:

1.        Smith                     1.01%
2.        Johnson               0.81
3.        Williams               0.70
4.        Jones                    0.62
5.        Brown                    0.62
6.        Davis                     0.48
7.        Miller                     0.42
8.        Wilson                  0.34
9.        Moore                    0.31
10.        Taylor                  0.31
11.        Anderson             0.31
12.        Thomas                0.31%