Recent excavation and analysis of the remaining section of the endangered Rapidan Mound site (44OR1) in the central Virginia Piedmont provide new insights into a unique complex of burial mounds in the Virginia interior. Known since Thomas Jefferson's eighteenth-century description, the mounds are both earth and stone and accretional earthen mounds. Thirteen are recorded, all dating to the late prehistoric and early contact era (ca. A.D. 900-1700). Typically containing few artifacts, the accretional mounds are unusual in North America in the numbers of individuals interred, more than one thousand in at least two cases, and in the nature of the secondary, collective burial ritual that built up the mounds over centuries. Following a review of the characteristics of the mound complex, we focus on the Rapidan Mound and the analysis of the collective, secondary burial features in the mound. Precise provenience information and bioarchaeological analyses of two large and intact collective burial features provide new information on health and diet, and several lines of evidence for demographic reconstruction. Finally, we discuss the mortuary ritual conducted at the mounds within the cultural and historical context of the region.