In 1974, the Canadian horror film Black Christmas hit the theatres and not only brought terror to the Holiday season, but revolutionized North American horror cinema in the process. Though, film history has generally giving John Carpenter’s Halloween the credit of creating the North American slasher film archetype, many film critics, film historians and horror fans recognize Black Christmas, which was released four years prior to Halloween, as the first film to set the slasher precedent for North American horror cinema.
[The Italian horror film genre Giallo is generally recognized as being the first wave of the slasher genre, but more on Giallo later!]
The Austin Chronicle has a nice review of the film from its release year in 06:
North Branch Library