Say what? Actually, it's a who:
It comes as no surprise that Elvis Presley, Ava Gardner, and Abraham Lincoln may be among their kin, yet the members of this tribe have never fitted properly into American racial categories. Depending on the census taker or tax man, they were classified as white, "free persons of color", or mulatto, often drifting across the color line as they moved from county to county....There are perhaps as many as 200,000 Melungeons in the United States today, all descended from a mysterious colony of olive-skinned people who lived for centuries in the foothills of the Appalachians. Some say the Melungeons can be traced back to Portuguese sailors, shipwrecked in the 16th century, or to colonial-era Turkish silk workers. Others point to Gypsies, to Sir Francis Drake's lost colony of Roanoke, or to the ancient Phoenicians. It's not even clear where the word Melungeon comes from: it might be derived from the French word mélange or even a corruption of an Arabic or Turkish term for "cursed souls".The article goes on to discuss attempts to research Melungeon heritage using DNA methods. This is a big deal because of the racial ambiguity - historically they have been been known to be taken to court for attempting to vote, or hanged for marrying white women.
One can see why Melungeons would have issues with racism, but then others aren't so sure they want to find their true ancestry. One researcher says he got a death threat from a Melungeon "repelled by the possibility of having African-American blood".
The article also mentions other groups similarly "isolated" genetically, such as Louisiana's Red Bones or the South Carolina Brass Ankles. Much more can be found here.