On the first night that the film crew arrived at the farm house location, an eerie fog rolled into the area. They quickly made use of this by shooting the outside of the house as this happened, and that footage was used for transitions throughout the film.
The house used for the exteriors of the Bishop house in the film still stands in Old Saybrook, Connecticut. Since its release in 1971, however, the house has been repainted and it now has a widow's walk on the roof.
The gravestone and summary of Venture Smith that Jessica quotes and does a rubbing of in the film is, in fact, a real grave. Its location is in a cemetery in Haddam, Connecticut.
The E. E. Dickinson Mansion in Essex, Connecticut was the house used for the interior scenes shown in the film.
Composer Orville Stoeber was paid with a new guitar for writing and performing the music score for the film.