Hi, there isn't a graveyard because it is memorial dedicated to the individuals who were hung on the spot during the witch hysteria of 1629. The reason for no graveyard is because it is said that after the people were hung their family members would come, under the cover of darkness, and recover the bodies. This site was verified as the execution site by a team of researchers from Salem State University's History Department and other historians.
I discovered more info about the project that brought this location to light through a Smithsonian Channel program called "America's Hidden Stories". This was covered in Season 1, Episode 1 and first aired 04th March 2019. The researchers discovered there is no grave site here, due to what others have already mentioned (family taking bodies away). For instance, accused "witch" John Proctor is actually buried somewhere near what's now a high school. I encourage all to watch the docuseries if they can access it. Really worth knowing the history. May the accused and deceased rest in peace.
Proctor's Ledge is located in a residential area, just behind a Walgreens outside of downtown Salem. There is another victims' memorial downtown that is near a graveyard- the second oldest in the US! You can visit Charter Street cemetery on your own during daylight hours or book a tour worth one of the numerous tour companies in town.
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