What Kanto Pokemon Only Evolve By Trade

Since Pokemon was first created, certain species can only Evolve when traded. This was first seen way back in the 1st Generation Pokemon Games, and it continued in Pokemon FireRed (and even continues to this very day). In the Kanto Pokedex, there are four Pokemon Species that can only evolve when traded: Kadabra (which evolves into Alakazam), Machoke (which evolves into Machamp), Graveler (which evolves into Golem), and Haunter (which evolves into Gengar). Of course, since trading is required, you will either need to trade for Kadabra, Machoke, Graveler or Haunter to obtain their Final Evolutions. That, or trade with someone to evolve these Pokemon and have them trade the Evolved Form back to you.

Additionally, after obtaining the National Pokedex, there will be more Pokemon that can only Evolve by being traded. However, these Pokemon require to be traded while holding an Evolutionary Item in order to evolve. These Pokemon include Poliwhirl (which will evolve into Politoed while holding the King's Rock), Slowpoke (which will evolve into Slowking while holding the King's Rock), Onix (which will evolve into Steelix while holding the Metal Coat), Scyther (which will evolve into Scizor while holding the Metal Coat), Seadra (which will evolve into Kingdra while holding the Dragon Scale), Porygon (which will evolve into Porygon2 while holding the Up Grade), Clamperl (which will evolve into Huntail while holding the DeepSeaTooth or into Gorebyss while holding the DeepSeaScale).