From Bulbapedia, the community-driven Pokémon encyclopedia.
Stone Town (Japanese: ストンタウン Stone Town) is a small village in Kanto located in between the Safari Zone and Cinnabar Island, at the foot of Evolution Mountain. It made its only anime appearance in The Battling Eevee Brothers.
The one part of Stone Town that sets it apart from other places is the fact that it is a popular place to evolve Pokémon with stones. When Ash and his friends arrived in Stone Town, they came across a party where Trainers from all around were evolving their Pokémon. The party was actually meant for Mikey, the youngest of the Eevee brothers, who had yet to evolve his Eevee. In the end, he decided to keep it the way it was, and the brothers eventually decided it was okay for him to do that.
Mikey's older brothers also tried to convince Brock and Ash to evolve their Vulpix and Pikachu, respectively. Both declined, saying they couldn't force their Pokémon to evolve.
Pokémon seen in Stone Town
In the manga
In The Electric Tale of Pikachu manga
Stone Town appears in the manga series The Electric Tale of Pikachu, which is based on the anime. Stone Town appears in the chapter To Evolve or Not to Evolve, That is the Question!, which is in turn based on The Battling Eevee Brothers. In the manga, Stone Town is located on an island named Dream Island.
Ash, Misty and Brock travel to Stone Town so that Misty could purchase a Water Stone for her Poliwhirl. Although she could not afford a stone, she was given one by Mikey, who gave it away because he was being pressured to evolve his Eevee to join the exclusive club "The Knights of the "E" Stone", which requires its members to own a Pokémon evolved by means of an evolutionary stone.