From information about an exhibit that took place in 2008 called Rest in Pieces:
Monument Cemetery, the second rural cemetery in Philadelphia, was founded in 1837 on North Broad Street, across from Temple University. In the 1950s, it fell victim to the school's need for parking lots. Thousands of those interred there were transferred to a mass grave in the suburbs. Their monuments were dumped into the Delaware River, where they are still visible today.
A wave of dizziness swept over me when I read that. What a shame. I'm not sure I would like to peer into the river and view the remains of all those tombstones. I generally like the peacefulness of a cemetery, whether my ancestors are buried there or not. But this is just eerie. And so sad.
My husband has ancestors whose graves were moved when the government used the right of eminent domain to create the Jefferson Proving Grounds. In that case the whole cemetery was moved, along with the monuments. His family was forced to leave their farmstead. But the graves of their ancestors can still be visited and great care was shown by moving them to another site. I wish the people of Philadelphia would have given the early residents of their city the same respect.