These are the eleven Pokemon from G/S/C that evolve from the original 151 from Kanto:
Crobat (Max Happiness on Golbat, and gaining a level)
Bellossom (Using Sun Stome on Gloom)
Espeon (Max Happiness with Eevee, level up during daytime)
Umbreon (Max Happiness with Eevee, level up during nighttime)
Slowking (Trading Slowpoke with a King's Rock)
Scizor (Trading Scyther with a Metal Coat)
Steelix (Trading Onix with a Metal Coat)
Kingdra (Trading Seadra with a Dragon Scale)
Blissey (Max Happiness with Chansey, gaining a level)
Porygon2 (Trading Porygon with a Up-grade)
Politoed (Trading Poliwhirl with a King's Rock)
If you meant in the wild, no none of these Pokemon are found in the wild. But they're pre-evolutions are, so you can always evolve these to get these Pokemon.
Here are their locations:
Golbat : Cerulean Cave, Icefall Cave, Lost Cave, Seafoam Islands
Gloom : Route 12, 13, 14, 15, Berry Forest, Bond Bridge, Cape Brink, Water Path
Poliwhirl : Route 6, 22, 23, 25, Cape Brink, Cerulean Cave, Four Island, Icefall Cave, Ruin Valley, Viridian City
Slowpoke : Route 4, 6, 10, 11, 12, 13, 19, 20, 21, 22, 23, 24, 25, Berry Forest, Bond Bridge, Canyon Entrance, Cape Brink, Celadon City, Cerulean Cave, Cerulean City, Cinnabar Island, Five Island, Five Isle Meadow, Four Island, Fuchsia City, Green Path, Icefall Cave, Kindle Road, Memorial Pillar, One Island, Outcast Island, Pallet Town, Resort Gorgeous, Ruin Valley, Seafoam Islands, Trainer Tower, Treasure Beach, Vermillion City, Viridian City, Water Labyrinth, Water Path (Wow -_-)
Onix : Rock Tunnel, Seavault Canyon
Chansey : Safari Zone Areas 2 & Center
Scyther : Safari Zone Areas 1 & Center (Only FireRed)
Eevee : Celadon City
Seadra : Bond Bridge, Cinnabar Island, Five Island, Five Isle Meadow, Green Path, Icefall Cave, Kindle Road, Memorial Pillar, One Island, Outcast Island, Pallet Town, Resort Gorgeous, Tanoby Ruins, Trainer Tower, Treasure Beach, Water Labyrinth, Water Path
Porygon : Celadon Game Corner 9999 Coins
EDIT : The Pokemon game will take you to the evolution screen, but it will seize evolving until you get the National Dex.
Source (Really you can shift between Crobat and any of the other said Pokemon for the fact.)
Hope I helped!