When the family is in the car at the beginning of the film and suspect something is happening, they cannot pick up any "CONELRAD" stations on the car's radio. CONELRAD (COntrol of ELectromagnetic RAdiation), established in 1951, was the first nationwide system for emergency broadcasts in the United States. All radios made between 1953 and 1963 were required to have marks on the AM dial at 640 and 1240 MHz where citizens were expected to tune to obtain civil defense information. CONELRAD was succeeded by the Emergency Broadcast System in 1963 (which did not use dedicated frequencies) and it, in turn, was replaced by the Emergency Alert System in 1997.
The Saddle Peak Lodge featured in the movie is an actual restaurant still open today. It is located in Calabasas, California, USA.
The film's trailer shows Marilyn Hayes (Joan Freeman) in the bedroom scene saying "Give me a gun. I'm good with a gun. I'll stay here and I'll kill them!". Those lines were cut from the completed film; judging by the position of her hands, the cut was probably made right after she says "They killed my mother and father."