While the current version of Gorilla City debuted in The Flash vol. 1 #106, the very first appearance of a location identified as Gorilla City occurred four years earlier in Congo Bill vol. 1 #6 (July 1955), by George Kashdan and Nick Cardy. The intelligent Gorillas in this story came from a "two mooned world" that Congo Bill assumed to be Mars.
After an alien spacecraft crashes into the jungles of Africa, local gorillas become hyper-intelligent and acquire telepathic abilities. These gorillas form Gorilla City. The city led by Solovar quickly creates technology far surpassing that of humanity and cloaks itself from human society. Flash first finds out about the city due to Gorilla Grodd, who probed Solovar's mind to find how to control minds, before trying to take over Gorilla City, then the world. However Flash defeated him. Gorilla Grodd took over the city briefly using neo-magnetic radiation. The radiation caused the rest of the gorillas to adore him, and they made him their king.
King Nnamdi - son of Solovar and current king of Gorilla City, he is telepathic like his father, isolationist.
King Solovar - deceased king of Gorilla City, he was a powerful telepath like Grodd, before being murdered by him.
King Ulgo - nephew of Solovar and his murderer, the intermediary successor before Nnamdi, not a telepath. He tried to use a device that turned humans into Gorillas, even transforming the JLA, but they were able to reverse the process.
Gorilla Grodd - an outcast from Gorilla City and a powerful telepath, who learned how to control minds by probing Solovar's mind, and was the first recurring foe of the second Flash. He plans to rule Gorilla City and the Earth.
Tolifhar - a former follower of Gorilla Grodd, and was the leader of his Gorilla Knights - a group of genetically modified white-furred gorillas made to fight superhumans. Wonder Woman was able to befriend Tolifhar, and they became allies. He and some of his gorilla brethren were guests in her home for some time. Can be identified from amongst his white gorilla brethren as the one with a scarred left eye. 
Gorilla City appears in The Flash episodes "Gorilla Warfare" and "Attack on Gorilla City". Flash and his team send Grodd to Earth-2, where he ends up at a remote sanctuary built for former ape test subjects, who have gained sufficient intelligence to establish a functioning, yet primitive, tribal society. Grodd is forced to serve their king, Solovar, who he eventually deposes with Flash's help and declares war on humanity.