|Information in this article is non-canon|
90 years before Littlefoot and his friends were born, the first dinosaurs migrated to the Great Valley . However, it was not uninhabited but, rather, was inhabited by Sharpteeth. Due to the fact that they knew, or rather believed, that the two couldn't coexist peacefully, the leaf eaters came and drove the Sharpteeth out. However, this was at great cost, as many leaf eaters, as well, as Sharpteeth, lost their lives. Indeed, the Old One was about 5 or so when the events happened. This caused her to greatly dislike Sharptooth, perhaps more so than Bron. Indeed, she says the terror of that day and the loss of many she loved caused her to never feel that the Great Valley would be her home (though, ironically, it would be her final resting place.). When the Sharpteeth, who were all Tyrannosauruses, fled, they left through a secret entrance/exit to the Great Valley that none of the leaf eaters knew about. In fact, the entrance was later overgrown and in a desert spot, somewhat near Saurus Rock.
The displayed carnivores eventually found the Valley of Sharpteeth. It was similar to the Great Valley, having many of the same plants that the Great Valley had, and, indeed, many that it didn't. However, it was hard to get to, the only entrance being concealed behind ivy. The other sides were surrounded by volancoes, though a wall similar to the Great Wall kept out any lava.
Leaf eaters didn't go there often, but, when they did, the inhabitants would hide and come out of hiding when the leaf eaters came in further to eat the plants, which could be spotted from the outside of the valley, and devour them. No leaf eater was allowed to escape.
The residents of the Valley of Sharpteeth had a strong loathing for the residents of the Great Valley, feeling they had stolen their home. There were some, unsuccessful, attempt to get back control of the Great Valley. The most notable was when they sent the Meanest Sharptooth to try and take out the leaf eaters, which may well have done great damage, had not The Lone Dinosaur taken him out. After the death of the Menest Sharptooth, no attempts were made ever again on the Great Valley and they gradually came to accept that the Valley of Sharpteeth was their home. However, they still didn't forgive the dinosaurs of the Great Valley as the years passed.
Much like the leaf eaters of the Mysterious Beyond and perhaps even early residents of the Great Valley were this way too, the Valley of Sharpteeth is highly segregated by species. In fact, the only species allowed in for 115 years was Tyrannosaurus Rex. It is noted by Sharptooth in the beginning of The Land Before Time XIV: The Terror of the Mysterious Beyond that the segregation was also prevalent in the Mysterious Beyond too among Sharpteeth as it was among leaf eaters.
Various Tyranosauruses lived here for over a century, unbothered by other Sharpteeth and able to work together to bring down any leaf eaters that entered the valley.
Andromeda was born and hatched here and grew up here. She would later bring in Chomper and Ruby. Chomper, being a fellow Tyranosaurus, was accepted, at least initially, at once. Ruby, however, being only half Sharptooth (omnviore), was likely only accepted to stay short term.
The reisdents were initially all against Red Claw, Screech, Thud, and Red Claw's other Fast Biters. However, after some, feeling irate that Andromeda turned them down for Chomper, and others, feeling that Chomper wasn't a proper sharptooth as he didn't eat regualr meat (i.e. other dinosaurs) like they did, eventually sided with Red Claw and Gallim.
Red Claw and his goons indeed inhabited the valley after taking it over, though they left to go fight in the Great Valley War, where all but Thud, who reformed, perished.
Andromeda's mother and father also lived in the Valley of Sharpteeth. It is implied that the daughter of Chomper and Andromeda, Susan, also comes to live here with her parents for a time when they are not living in the Great Valley.
Chmper visited it, as did Ruby. Ruby, as stated earlier, was allowed mainly temporary status, as she was only an omnviore and not a Tyranosaurus. Ruby questioned the herd segreation, as did Chomper, which irritated many, though it intrigued Andromeda.
Red Claw and his crew also came and assumed leadership of the valley, though he was ultimately, even if he didn't know it, a puppet for Gallim, the Terror of the Mysterious Beyond.
Littlefoot, Cera Ducky, Petrie, Perrin, Ali, Spike, Ruby, Ralph, and other love interests of the characters visited here. They no doubt would have been killed and eaten without mercy, had not Red Claw, urged by Sierra, given the order not to harm them, though to chase them to make it look like they were after them, but really they were hoping that the leaf eaters would lead them to Chomper and Andromeda, whom Red Claw and Gallim greatly wanted dead.
Though the residents normally didn't have much to do with outsiders, some took the side of Red Claw and Gallim. Others, led by Andromeda and her family, as well as Chomper, eventually agreed to aide the long time enemies, the dinoaurs of the Great Valley, in the Great Valley War against Gallim and his minions. After the war, the two valleys made peace, though, due to the obvious difference in their diets, they still didn't make much contact afterward.
After the Great Valley War was over, Chomper and Andromeda assumed a leadership role in the valley. As such, the two ended the segregaton policy, allowing Fast Biters, Belly Draggers, Giganotosauruses, Sharp Beaks, Albertosauruses , Daspletosaurus and others into the valley.
Leaf eaters, though specifically Littlefoot and the gang and their families, as the Sharpteeth did still attack others that came unbidden, were allowed in unharmed and could eat of the plants there, which they greatly enjoyed.
In the end, the Valley of Sharpteeth became the Sharptooth counterpart of the Great Valley, allowing diferent herds that worked together, to reside there. Also, for the first time, friendships developed across species lines.
Also, though most of the residents saw leaf eaters best as food, they either respected Littlefoot for having defeated Gallim, or Chomper, for having defeated Red Claw, to not dare try and eat them. Or, perhaps they knew enough members of the valley did respect one or both of Littlefoot and Chomper and knew they couldn't get away with trying to eat them and so didn't try.