Dragonwyck is a 1946 film directed by Joseph Mankiewicz and starring Gene Tierney, Vincent Price, Walter Huston, Spring Byington, Anne Revere, Harry Morgan and Jessica Tandy. It's more gothic romance than horror, but it shows up in some of the horror film lists I've seen.
Youtube has it online divided into 10 sections. part 1:
part 2, part 3, part 4, part 5, part 6, part 7, part 8, part 9, part 10
The New York Times gives it a negative review and closes by saying, "The settings and costumes are intriguing. Not as much can be said for "Dragonwyck."" Variety describes it as a "lucid, often-compelling" film version of the book on which it's based. DVDTalk reviews it as part of a 4-film set. TCM has an overview.