Although not the first werewolf film, this is considered to be the first feature length werewolf movie. It preceded the more commercially successful The Wolf Man (1941) by six years. The first werewolf film was the 1913 short "The Werewolf". It was 18 minutes long and now considered lost as all known copies were destroyed in a warehouse fire in 1924.
This film made up much of its werewolf mythology out of whole cloth. The ideas that being bitten by a werewolf makes one a werewolf, that a werewolf changes under the full moon, and that werewolves were wolf/man hybrids were completely made up. In folklore, one becomes a werewolf deliberately by practicing witchcraft and can change into a wolf at any time desired. This film's mythology, and that of others after it, heavily influenced pop culture views of werewolves to the point that these are now regarded as "official" mythology.
The werewolf howl used in this film is a combination of Henry Hull's own voice and a recording of an actual timber-wolf. The result is generally thought to have a far more realistic result than in any subsequent werewolf films, including The Wolf Man (1941).
The copyright record synopsis has a scene where a boy is almost eaten by a plant in the botanical gardens sequence, and he is saved by Wilfred. It was not included in the final print.
The opening scene in "Tibet" was filmed at Vasquez Rocks north of Los Angeles, well know to Star Trek (1966) fans as the rock outcropping from where Captain Kirk rolled a boulder down trying to kill the Gorn in Arena (1967).