Megan Smolenyak has written an interesting article that provides a lot of information about Michelle Obama's ancestry. Michelle, daughters Malia and Sasha, and her mother, Marian (Shields) Robinson, are the first descendants of slaves to reside at 1600 Pennsylvania Avenue as members of the first family.
Megan tells of Michelle's great-great-grandfather, Dolphus Shields and his mother, Melvina McGruder. Dolphus was born into slavery, yet lived long enough to overlap the life of a White House-bound descendant.
While every southern state except Florida, Arkansas and Texas can claim a piece of the First Lady's past, no place holds more of it than Henry and Pittsylvania counties in Virginia. Fully a quarter of her ancestry traces to this region. Were she to visit Martinsville or Danville, she would be walking among more hidden cousins than anyplace else other than Chicago where the various branches of her family eventually intertwined due to the Great Migration.
You can read this interesting article and also view images of some of the original records at http://www.huffingtonpost.com/megan-smolenyak-smolenyak/michelle-obamas-roots-col_b_470296.html.