The exterior for the Marsten House was actually a full-scale facade built upon a smaller pre-existing hill-top house. In total, the facade cost the production an estimated $100,000 dollars to build. In 1979, an entire house (including the interiors) could have been made for that amount.
Director George A. Romero was originally approached to direct a feature film version, but after the announcements of John Badham's Dracula (1979) and Werner Herzog's Nosferatu the Vampyre (1979), Warner Bros. decided to turn Salem's Lot into a TV mini-series. Romero dropped out, feeling he wouldn't be able to make the film the way he wanted to with the restrictions of network television.
Although this adaptation differs dramatically in a lot of different areas from the novel - notably in the depiction of chief vampire Mr Barlow - Stephen King approved of it.
James Mason jumped at the chance of playing a servant of evil, loving the script. This was fortunate as he was producer Richard Kobritz's first choice for the role of Mr Straker.
The original intent was for Warner Brothers to turn Stephen King's 400 page bestseller into a feature film. Stirling Silliphant, Robert Getchell and Larry Cohen all had a go at distilling the material down to two hours' length but none of these were deemed to capture the essence of the novel. Eventually the project was handed over to Warner Brothers Television where producer Richard Kobritz felt it would work better as a TV mini-series.