In the colonial years, while conditions were more fluid, white women, indentured servant or free, and African men, servant, slave or free, made unions. Because the women were free, their mixed-race children were born free; they and their descendants formed most of the families of free people of color during the colonial period in Virginia. The scholar Paul Heinegg found that eighty percent of the free people of color in North Carolina in censuses from 1790–1810 could be traced to families free in Virginia in colonial years.
Is there an answer to this question (If it cannot be answered, say "unanswerable"): What censuses did he study?
from 1790–1810