Many were buried in contagious hospitals, near workhouses and etc. also records to look into. Salem MA had these as well the contagious hospital was near the Salem Willows behind the contagious hospital there was also a cave that held bodies no markers and the cemetery. Those graves were never kept up either and now condos stand next to the area. Though I had not thought of this in many years wonder what they did with the bodies? Many graves in cemeteries have no makers either but some of us had families that never threw anything away like plot records. My great grandparents had no markers for almost a hundred years though we went to Ipswich every year to put flowers. The greats died very young first David, then Nora and my grandfather was only 15, he had a choice of either keeping his brother with him by working or a grave stone, he picked his brother. This is why many had no stones but today many have put stones on these graves for they are part of our families and of history even if only a small part of the past, they are our past.