Shot entirely on location. There are no interior shots in the film at all.
Shot for under $100,000, American International Pictures picked it up cheaply and made a healthy profit out of it at the drive-in theaters.
In an interview with Quentin Tarantino, Dennis Hopper claimed that this film was his first real directorial effort, in that his behavior drove director Anthony M. Lanza to quit, after which Hopper ended up directing the film.
The path that Darryl and Chris walk down by the lake is the same one used for the intro to The Andy Griffith Show (1960). It is situated next to Franklin's Canyon Reservoir of the 600 acre park in upper Beverly Hills. The boulders that Andy and Opie pass are still there, but have been rearranged, and re-oriented around the area.