The second Flash Barry Allen first came into conflict with Grodd in the early days of his career as a Super-Hero. While he had already encountered criminals like Captain Cold and the Weather Wizard, Grodd was on another level compared to the villains he had encountered before. Solovar, an ape from the hidden Gorilla City, was pretending to be a regular gorilla in the Central City Zoo, when he contacted the Flash to warn him of Grodd's plans to conquer the human world.
He explained to the Flash how he and his people came to be, telling him that he was once a regular ape until an alien spacecraft crashed in his African jungle home. The local tribe of apes were then changed when the ship's alien pilot granted them incredible intelligence and mental powers, giving them all telepathy and telekinesis. The alien then helped them all build Gorilla City, where the apes chose to live in peace, apart from humanity, with technology more advanced than any human's. But the gorilla named Grodd was corrupt, and believed that the apes should take over humanity, and appointment him as their ruler.
There the residents of Gorilla City lived in peace for many years until their home was discovered by a group of explorers. Grodd then forced one of the explorers to kill the alien who granted them their powers, and he took over Gorilla City, from where he planned to take over the entire world. The ape Solovar journeyed to the outside world for help, and contacted Barry Allen to warn him of the evil gorilla's plans. Once Grodd was defeated by the Flash, he was able to temporarily remove Grodd's mental powers.
Grodd's powers eventually returned, and for the next several years he makes many attempts at destroying the Flash, with schemes involving transferring his mind into that of a human being (alternately named Drew Dowdon or William Dawson), taking away the intelligence of his fellow apes from Gorilla City, and even faking his own death, and transferring his mind into that of a regular ape from the Central City Zoo. When fighting the Flash solo didn't pan out for him, he would team up with several other world conquering villains on many different teams, but he always wound up defeated and imprisoned by the Scarlet Speedster.
After the events of the Crisis on Infinite Earths, Barry Allen died saving the universe, and the mantle of the Flash was passed on to his nephew and former partner Wally West. Gorilla Grodd then attempted many schemes against Wally West just as he did with his mentor Barry Allen. One of Grodd’s most elaborate plans to conquer the world was to arrange King Solovar's assassination, and then manipulate the inhabitants of Gorilla City into war against the human world. He tried to accomplish this with the help of a secret organization of powerful and corrupt apes called Simian Scarlet. But in his hubris, Grodd absorbs too much mental energy from the apes of Gorilla City, and he is left with the intelligence level of a normal gorilla. Although he eventually recovered, he was then placed in a special wing of the prison called Iron Heights.
It was also Grodd who was responsible for Hunter Zolomon's crippling, resulting in the man's transformation into the villainous Zoom after trying to change the past and prevent his own injury. Zoom then became one of Wally West’s greatest adversaries.Grodd once again teamed up with several of the villainous elite of the DC Universe, working with the likes of Lex Luthor and even the Joker. He was also a member of the terrorist group known as Tartarus, who fought against Wally West's team the Titans.
After the events of 2011's FLASHPOINT, reality was altered, and so was much of Grodd's personal history. In this new timeline, Grodd was raised by the village Elders in Gorilla City, who believed him to be the chosen one who would receive something called "The Light," which was the ancient power which altered their gorilla ancestor's minds and evolving them to what they became (and which humans call the Speed Force). The apes of Gorilla City believed that when the Messenger of The Light arrived, he would be able to bring in a new age for Gorilla City.
When the twisted young Grodd finally came of age, he challenged his father, King Grodd, to a life or death fight, the survivor of which would rule over Gorilla City. Father and son fought, but the younger Grodd had no mercy for his father, and killed him. Proclaiming himself the new King Grodd, he ate his father's brain, thereby acquiring all of his knowledge and memories. A terrified Gorilla City was ready to bow before their new king.
Not long after this moment however, after travelling through the Speed Force, Barry Allen (now alive again in this new reality) finds himself in Gorilla City. Seen by the apes of the hidden metropolis as the messenger from an ancient prophecy that heralded him as the Bringer of Light, many apes were now skeptical of Grodd really being the chosen one. Seen as a threat to his rise to power, Grodd tried to have the Flash murdered.
Although seemingly defeated, Grodd would return again and again to seek his revenge against the Flash, sometimes alone, and sometimes with other villainous allies. After trying to take over Central City and enslaving its population, Barry eventually drags Grodd into the Speed Force itself, during which time Solovar takes over as King of Gorilla City and attempts to repair the apes' relationship with the human world. Grodd eventually escaped, becoming an ever present threat to the Flash family, and the entire world.