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 Kurt 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.
Stephen King was inspired to write the book when he had his English class read "Dracula", and became curious about what would happen if vampires came to America, specifically in a small town.