Gorgo was made at the behest of the King Brothers, two US producers who made a number of B Westerns in the previous decade and would subsequently make Captain Sindbad (1963). Lourie is also working with less resources in terms of effects budget than he was on his other dinosaur two films where they created their dinosaurs via the time-consuming stop-motion animation process, here he resorts to the good old man in a monster suit as has been patented a few years earlier by Godzilla, King of the Monsters (1954). That said, Gorgo emerges as the best of Eugene Louries dinosaur films due to the fact that it gives the rampaging monster story an entirely different spin and a surprise twist of sympathy.
One of the other bonuses about Gorgo is that it is the only of Eugene Louries films to have been made in colour. Lourie has gone to shoot on the Irish coast and this lends itself to some visually impressive location photography. The characters are drawn somewhat better than usual in these films. Lourie creates some good set-pieces Bill Travers descent by bathysphere and encountering the Gorgo in the depths; or the scene where the Gorgo is initially taken to London and manages to get free as they transfer it to the carnival. In the middle of the film, Lourie also does a fine job of integrating what is clearly footage of the British Navy on manoeuvres this is certainly blended with opticals and original footage far better than it is in a comparable film like Invaders from Mars (1953).
When the invasion of London comes during the films last quarter, Lourie pulls off his best effects set-pieces the demolition of the Tower Bridge; the mother Gorgo towering over Big Ben backlit by orange smoke, demolishing the clock as the military fire missiles at her. There is an enormous sense of convincing panic created as the monster starts trampling the crowds and people are forced to take refuge in the subway. Even though the effects are down around the level of the average late 1950s Godzilla film, you tend to forget it is a man in a monster suit and be impressed by the sheer spectacle on display. What we end up with is a superior monster movie.
The plot for the first half of Gorgo has been borrowed from King Kong (1933) the monster that is captured and taken to be exhibited in the city whereupon it proceeds to escape and go amok. The touch that makes the film stand out is the revelation in the last third that the dinosaur they have captured is only an infant and that the mother has arrived to get her child back and is very angry. This gives an extra level of poignancy to the film the final image the film goes out on with the mother and child by her side walking into The Thames as London burns around them is a beautiful one. It makes the antagonistic force of the film something strikingly different as opposed to a rampaging monster that only needs be exterminated by the forces of law and order.
The idea of the monster and its child was promptly borrowed by Toho for the Godzilla series in Son of Godzilla (1968) wherein Godzilla almost identically gained a son, although that was played as far more of a cutsie childrens film. A rival Japanese company stole the basic plot for their monster movie Monster from a Prehistoric Planet/Gappa the Triphibian Monster (1967).