Hello Greta,

Since you have traced your great-great-grandmother, Lucinda Underwood, back to the 1870 census for Wilson County, Tennessee, and you know her parents' names, then you should continue your search in the 1860 or earlier census records to see if any of them are listed. If either of her parents or Lucinda is found in a census prior to 1870, that person was almost certain to have been a free person of color. Good luck.

Regards,
Sandra