Cathy, are you sure they moved away? I think they were still in Rockbridge as late as the 1840's. The 1841 tax list indicates the following people with surname "Black": James, John, William B. - William, Benjamin - Joseph. The dash indicates a separate "district". Only Benjamin and William B. were in the 1850 census. My take is that William, Joseph, John and James probably died between 1841 and 1850. It seems unlikely to me that John would leave since he inherited Henry's land.