Piedras Blancas (Spanish for "White Rocks") actually exists. It's a town on the central California coast, and it does have a lighthouse that was used in this film, but only for exterior shots. The same lighthouse was used for exterior shots in Brave New World (1980).
The exterior and interior lighthouse location used in the film is the Point Conception Lighthouse in California. The same location was used in the 1980 film series Brave New World, directed by Burt Brinckerhoff and based on Aldous Huxley's best known 1932 novel 'Brave New World'.
The Monster is described as a member of the real-world Diplovertebron family. Diplovertebrons were an extinct genus of Anthracosauria (Labyrinthodont) that lived in the Late Carboniferous period (Moscovian) some 300 million years ago. They were medium-sized amphibians, 60 cm in length, with triangular-shaped skulls similar to those of crocodiles. Newspaper reports of fossil examples found in Pennsylvania during the late 1950s may possibly have inspired the scriptwriter of this film.
In 1965 the monster costume for this film was used in Flipper: Flipper's Monster (1965), in which film crew is shooting a "monster movie" in Florida. That episode was directed by Ricou Browning, the show's creator, who coincidentally was best known for playing the "Gill-Man" in Creature from the Black Lagoon (1954), which was the inspiration for "Monster of Piedras Blancas".