The first burial is listed as 1842. But was the cemetery actually established at that time? I have an ancestor who was moved from the Stonington area to Oak Grove cemetery in Springfield in 1870. I expect she was moved from a homesteader's graveyard. I don't believe she would have been moved had she been initially interred at Old Stonington Cemetery.
She arrived at Old Stonington in 1839. Her date of death is unknown.