In his book The Claims of Kinfolk (2003), he elucidates the informal customs that slaves in the antebellum South used to recognize ownership of property, even while they were themselves considered by law to be property at the time. He also traces the interactions of these extra-legal, vernacular customs with the formal realm of law after emancipation by teasing stories of claims and disputes from such sources as the Freedman’s Bureau and Southern Claims Commission records compiled by the federal government after the Civil War. In addition to demonstrating that ownership of land, livestock, and other material possessions was much more widespread among slave communities than previously believed, Penningroth’s research draws out the underlying social relations and reliance on family members’ labor that made such ownership possible.

I'm going to have to watch this when I have more time to focus, but it's clear that he has patched together an intricate social network from 150+ years ago.