From the New York Times:
WASHINGTON — In 1850, the elderly master of a South Carolina estate took pen in hand and painstakingly divided up his possessions. Among the spinning wheels, scythes, tablecloths and cattle that he bequeathed to his far-flung heirs was a 6-year-old slave girl valued soon afterward at $475.
In his will, she is described simply as the “negro girl Melvinia.” After his death, she was torn away from the people and places she knew and shipped to Georgia. While she was still a teenager, a white man would father her first-born son under circumstances lost in the passage of time.
http://cdn.newsone.com/external/js/gallery/61991 In the annals of American slavery, this painful story would be utterly unremarkable, save for one reason: This union, consummated some two years before the Civil War, represents the origins of a family line that would extend from rural Georgia, to Birmingham, Ala., to Chicago and, finally, to the White House. Melvinia Shields, the enslaved and illiterate young girl, and the unknown white man who impregnated her are the great-great-great-grandparents of Michelle Obama, the first lady.
Viewed by many as a powerful symbol of black advancement, Mrs. Obama grew up with only a vague sense of her ancestry, aides and relatives said. During the presidential campaign, the family learned about one paternal great-great-grandfather, a former slave from South Carolina, but the rest of Mrs. Obama’s roots were a mystery.