From trail/film maven Paul Ayers:
As most film buffs know John Carpenter’s 1978 classic Halloween, which more or less created the slasher movie genre, was shot all over the San Gabriel Valley with location shooting in Sierra Madre, Pasadena and South Pasadena. Less known is the Altadena location of a scene in the film where Dr. Sam Loomis [played by the late, great Donald Pleasance] emerges from the offices of the Warren County Sanitarium, where he has been trying to convince the staff that Michael Myers is on his way to Haddonfield, Illinois to wreak havoc, walks down to the parking lot and drives off in a high dudgeon.
The first shot gives it away as Dr. Loomis steps right onto mat inscribed with the location’s real name, “La Vina”. Yes, the scene was shot at the old La Vina Respiratory Hospital now the site of the La Vina housing development. Below are shots from the scene and a orienting photo of the hospital from the 1970s.