Route 22: 29 species in 8 games

Road 22: 29 species across 14 versions

Red and Green (Japan): 7 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	2 to 4	45%	All places
Spearow	Walking in tall grass or a cave	3 to 5	10%	All places
Nidoran♀	Walking in tall grass or a cave	3 to 4	5%	All places
Nidoran♂	Walking in tall grass or a cave	2 to 4	40%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Poliwag	Fishing with a super rod	15	50%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Goldeen	Fishing with a super rod	15	50%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Red and Blue: 7 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	2 to 4	45%	All places
Spearow	Walking in tall grass or a cave	3 to 5	10%	All places
Nidoran♀	Walking in tall grass or a cave	3 to 4	5%	All places
Nidoran♂	Walking in tall grass or a cave	2 to 4	40%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Poliwag	Fishing with a super rod	15	50%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Goldeen	Fishing with a super rod	15	50%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Yellow: 9 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	3	10%	All places
Spearow	Walking in tall grass or a cave	2 to 6	10%	All places
Nidoran♀	Walking in tall grass or a cave	2 to 4	30%	All places
Nidoran♂	Walking in tall grass or a cave	2 to 4	30%	All places
Mankey	Walking in tall grass or a cave	3 to 5	20%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Poliwag	Fishing with a super rod	5 to 15	90%	All places
Poliwhirl	Fishing with a super rod	15	10%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Gold: 8 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	3 to 7	up to 95%	All places
Spearow	Walking in tall grass or a cave	3 to 5	up to 50%	All places
Fearow	Walking in tall grass or a cave	7	up to 5%	All places
Poliwag	Fishing with a good rod	20	65%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Poliwag	Surfing	4 to 14	90%	All places
Poliwhirl	Surfing	10 to 14	10%	All places
Ponyta	Walking in tall grass or a cave	6	up to 5%	All places
Doduo	Walking in tall grass or a cave	4	up to 10%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places

Silver: 8 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	3 to 7	up to 95%	All places
Spearow	Walking in tall grass or a cave	3 to 5	up to 50%	All places
Fearow	Walking in tall grass or a cave	7	up to 5%	All places
Poliwag	Fishing with a good rod	20	65%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Poliwag	Surfing	4 to 14	90%	All places
Poliwhirl	Surfing	10 to 14	10%	All places
Ponyta	Walking in tall grass or a cave	6	up to 5%	All places
Doduo	Walking in tall grass or a cave	4	up to 10%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places

Crystal: 8 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	3 to 7	up to 60%	All places
Spearow	Walking in tall grass or a cave	3 to 5	up to 50%	All places
Fearow	Walking in tall grass or a cave	7	up to 5%	All places
Poliwag	Fishing with a good rod	20	65%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Poliwag	Surfing	4 to 14	90%	All places
Poliwag	Walking in tall grass or a cave	3 to 4	40%	All places
Poliwhirl	Surfing	10 to 14	10%	All places
Ponyta	Walking in tall grass or a cave	6	up to 5%	All places
Doduo	Walking in tall grass or a cave	4	up to 10%	All places
Magikarp	Fishing with a good rod	20	35%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places

FireRed: 9 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	2 to 5	45%	All places
Spearow	Walking in tall grass or a cave	3 to 5	10%	All places
Psyduck	Fishing with a super rod	15 to 35	5%	All places
Psyduck	Surfing	20 to 40	100%	All places
Mankey	Walking in tall grass or a cave	2 to 5	45%	All places
Poliwag	Fishing with a good rod	5 to 15	60%	All places
Poliwag	Fishing with a super rod	15 to 25	40%	All places
Poliwhirl	Fishing with a super rod	20 to 30	40%	All places
Goldeen	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with an old rod	5	100%	All places
Gyarados	Fishing with a super rod	15 to 25	15%	All places

LeafGreen: 9 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	2 to 5	45%	All places
Spearow	Walking in tall grass or a cave	3 to 5	10%	All places
Mankey	Walking in tall grass or a cave	2 to 5	45%	All places
Poliwag	Fishing with a good rod	5 to 15	60%	All places
Poliwag	Fishing with a super rod	15 to 25	40%	All places
Poliwhirl	Fishing with a super rod	20 to 30	40%	All places
Slowpoke	Fishing with a super rod	15 to 35	5%	All places
Slowpoke	Surfing	20 to 40	100%	All places
Goldeen	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with a good rod	5 to 15	20%	All places
Magikarp	Fishing with an old rod	5	100%	All places
Gyarados	Fishing with a super rod	15 to 25	15%	All places

HeartGold and SoulSilver: 16 species
Species	Method	Levels	Chance	Game page
Rattata	Walking in tall grass or a cave	3 to 7	up to 35%	All places
Spearow	Walking in tall grass or a cave	3 to 5	up to 30%	All places
Fearow	Walking in tall grass or a cave	7	up to 5%	All places
Poliwag	Fishing with a good rod	20	60%	All places
Poliwag	Fishing with an old rod	10	15%	All places
Poliwag	Fishing with a super rod	40	80%	All places
Poliwag	Surfing	5 to 10	90%	All places
Poliwhirl	Surfing	10	10%	All places
Ponyta	Walking in tall grass or a cave	6	5%	All places
Doduo	Walking in tall grass or a cave	4	up to 10%	All places
Magikarp	Fishing with a good rod	20	40%	All places
Magikarp	Fishing with an old rod	10	85%	All places
Magikarp	Fishing with a super rod	40	20%	All places
Hoothoot	Headbutting trees	3 to 7	up to 50%	All places
Spinarak	Headbutting trees	5 to 7	30%	All places
Pineco	Headbutting trees	3 to 4	30%	All places
Linoone	Walking in tall grass or a cave	5	20%	All places
Wurmple	Headbutting trees	3 to 7	up to 20%	All places
Whismur	Walking in tall grass or a cave	3	20%	All places
Bidoof	Walking in tall grass or a cave	5	20%	All places
Buizel	Walking in tall grass or a cave	3	20%	All places

Let's Go, Pikachu and Eevee: 13 species
Species	Method	Levels	Chance	Game page
Charizard	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Rattata	Walking in the overworld	3 to 4	100%	All places
Spearow	Walking in the overworld	3 to 4	100%	All places
Spearow	Flying pokemon in the sky	3 to 56	100%	All places
Fearow	Flying pokemon in the sky	3 to 56	100%	All places
Nidoran♀	Walking in the overworld	3 to 4	100%	All places
Nidoran♂	Walking in the overworld	3 to 4	100%	All places
Poliwag	Surfing in the overworld	3 to 4	100%	All places
Poliwhirl	Surfing in the overworld	3 to 4	100%	All places
Magikarp	Surfing in the overworld	3 to 4	100%	All places
Articuno	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Zapdos	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Moltres	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Dragonite	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places