Route 24: 39 species in 8 games

Red and Green (Japan)Red and Blue Yellow Gold and Silver Crystal FireRed and LeafGreen HeartGold and SoulSilver Let's Go, Pikachu and Eevee

Road 24: 39 species across 14 versions

Red and Green (Japan): 10 species
Species	Method	Levels	Chance	Game page
Caterpie	Walking in tall grass or a cave	7	20%	All places
Metapod	Walking in tall grass or a cave	8	20%	All places
Pidgey	Walking in tall grass or a cave	12 to 13	20%	All places
Psyduck	Fishing with a super rod	15	33%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Abra	Walking in tall grass or a cave	8 to 12	15%	All places
Bellsprout	Walking in tall grass or a cave	12 to 14	25%	All places
Krabby	Fishing with a super rod	15	33%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Goldeen	Fishing with a super rod	15	34%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Red and Blue: 10 species
Species	Method	Levels	Chance	Game page
Caterpie	Walking in tall grass or a cave	7	20%	All places
Metapod	Walking in tall grass or a cave	8	20%	All places
Pidgey	Walking in tall grass or a cave	12 to 13	20%	All places
Psyduck	Fishing with a super rod	15	33%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Abra	Walking in tall grass or a cave	8 to 12	15%	All places
Bellsprout	Walking in tall grass or a cave	12 to 14	25%	All places
Krabby	Fishing with a super rod	15	33%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Goldeen	Fishing with a super rod	15	34%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Yellow: 10 species
Species	Method	Levels	Chance	Game page
Charmander	Receive as a gift	10	100%	All places
Pidgey	Walking in tall grass or a cave	13 to 17	29%	All places
Pidgeotto	Walking in tall grass or a cave	17	1%	All places
Oddish	Walking in tall grass or a cave	12 to 14	30%	All places
Venonat	Walking in tall grass or a cave	13 to 16	10%	All places
Poliwag	Fishing with a good rod	10	50%	All places
Bellsprout	Walking in tall grass or a cave	12 to 14	30%	All places
Goldeen	Fishing with a good rod	10	50%	All places
Goldeen	Fishing with a super rod	20 to 30	90%	All places
Seaking	Fishing with a super rod	30	10%	All places
Magikarp	Fishing with an old rod	5	100%	All places

Gold and Silver: 10 species
Species	Method	Levels	Chance	Game page
Oddish	Walking in tall grass or a cave	10	30%	All places
Venonat	Walking in tall grass or a cave	8	up to 30%	All places
Venomoth	Walking in tall grass or a cave	10	5%	All places
Abra	Walking in tall grass or a cave	9	up to 20%	All places
Bellsprout	Walking in tall grass or a cave	8 to 10	up to 60%	All places
Weepinbell	Walking in tall grass or a cave	12 to 14	up to 15%	All places
Goldeen	Fishing with a good rod	20	65%	All places
Goldeen	Fishing with an old rod	10	15%	All places
Goldeen	Fishing with a super rod	40	70%	All places
Goldeen	Surfing	4 to 14	90%	All places
Seaking	Fishing with a super rod	40	10%	All places
Seaking	Surfing	10 to 14	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
Sunkern	Walking in tall grass or a cave	10	30%	All places

Crystal: 12 species
Species	Method	Levels	Chance	Game page
Caterpie	Walking in tall grass or a cave	8 to 10	up to 60%	All places
Metapod	Walking in tall grass or a cave	12	20%	All places
Butterfree	Walking in tall grass or a cave	14	up to 5%	All places
Oddish	Walking in tall grass or a cave	10 to 12	50%	All places
Gloom	Walking in tall grass or a cave	14	5%	All places
Venonat	Walking in tall grass or a cave	10	30%	All places
Abra	Walking in tall grass or a cave	12	up to 10%	All places
Bellsprout	Walking in tall grass or a cave	10	up to 5%	All places
Goldeen	Fishing with a good rod	20	65%	All places
Goldeen	Fishing with an old rod	10	15%	All places
Goldeen	Fishing with a super rod	40	70%	All places
Goldeen	Surfing	4 to 14	90%	All places
Seaking	Fishing with a super rod	40	10%	All places
Seaking	Surfing	10 to 14	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
Sunkern	Walking in tall grass or a cave	12	30%	All places

FireRed: 13 species
Species	Method	Levels	Chance	Game page
Caterpie	Walking in tall grass or a cave	7	20%	All places
Metapod	Walking in tall grass or a cave	8	1%	All places
Weedle	Walking in tall grass or a cave	7	20%	All places
Kakuna	Walking in tall grass or a cave	8	4%	All places
Pidgey	Walking in tall grass or a cave	11 to 13	15%	All places
Oddish	Walking in tall grass or a cave	12 to 14	25%	All places
Psyduck	Fishing with a super rod	25 to 35	1%	All places
Abra	Walking in tall grass or a cave	8 to 12	15%	All places
Tentacool	Surfing	5 to 40	100%	All places
Krabby	Fishing with a good rod	5 to 15	20%	All places
Horsea	Fishing with a good rod	5 to 15	60%	All places
Horsea	Fishing with a super rod	15 to 35	84%	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: 13 species
Species	Method	Levels	Chance	Game page
Caterpie	Walking in tall grass or a cave	7	20%	All places
Metapod	Walking in tall grass or a cave	8	4%	All places
Weedle	Walking in tall grass or a cave	7	20%	All places
Kakuna	Walking in tall grass or a cave	8	1%	All places
Pidgey	Walking in tall grass or a cave	11 to 13	15%	All places
Abra	Walking in tall grass or a cave	8 to 12	15%	All places
Bellsprout	Walking in tall grass or a cave	12 to 14	25%	All places
Tentacool	Surfing	5 to 40	100%	All places
Slowpoke	Fishing with a super rod	25 to 35	1%	All places
Krabby	Fishing with a good rod	5 to 15	60%	All places
Krabby	Fishing with a super rod	15 to 35	84%	All places
Horsea	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: 14 species
Species	Method	Levels	Chance	Game page
Oddish	Walking in tall grass or a cave	10	up to 20%	All places
Venonat	Walking in tall grass or a cave	8	up to 20%	All places
Venomoth	Walking in tall grass or a cave	14	5%	All places
Abra	Walking in tall grass or a cave	9	20%	All places
Bellsprout	Walking in tall grass or a cave	8 to 10	up to 40%	All places
Weepinbell	Walking in tall grass or a cave	12 to 14	up to 10%	All places
Goldeen	Fishing with a good rod	20	60%	All places
Goldeen	Fishing with an old rod	10	15%	All places
Goldeen	Fishing with a super rod	40	70%	All places
Goldeen	Surfing	5 to 10	90%	All places
Seaking	Fishing with a super rod	40	10%	All places
Seaking	Surfing	10	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
Sunkern	Walking in tall grass or a cave	10	up to 20%	All places
Linoone	Walking in tall grass or a cave	9	20%	All places
Whismur	Walking in tall grass or a cave	8 to 10	20%	All places
Bidoof	Walking in tall grass or a cave	9	20%	All places
Buizel	Walking in tall grass or a cave	8 to 10	20%	All places

Let's Go, Pikachu: 16 species
Species	Method	Levels	Chance	Game page
Charmander	Receive as a gift	14	100%	All places
Charizard	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Squirtle	Rare spawn in grass with lure or catch combo	7 to 12	100%	All places
Pidgey	Walking in the overworld	7 to 12	100%	All places
Pidgey	Flying pokemon in the sky	3 to 56	100%	All places
Pidgeotto	Flying pokemon in the sky	3 to 56	100%	All places
Pidgeot	Flying pokemon in the sky	3 to 56	100%	All places
Oddish	Walking in the overworld	7 to 12	100%	All places
Venonat	Walking in the overworld	7 to 12	100%	All places
Psyduck	Walking in the overworld	7 to 12	100%	All places
Tentacool	Surfing in the overworld	7 to 12	100%	All places
Tentacruel	Surfing in the overworld	7 to 12	100%	All places
Magikarp	Surfing in the overworld	7 to 12	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

Let's Go, Eevee, Let's Go, Pikachu and Eevee: 17 species
Species	Method	Levels	Chance	Game page
Charmander	Receive as a gift	14	100%	All places
Charizard	Rare spawn in the sky with lure or catch combo	3 to 56	100%	All places
Squirtle	Rare spawn in grass with lure or catch combo	7 to 12	100%	All places
Pidgey	Walking in the overworld	7 to 12	100%	All places
Pidgey	Flying pokemon in the sky	3 to 56	100%	All places
Pidgeotto	Flying pokemon in the sky	3 to 56	100%	All places
Pidgeot	Flying pokemon in the sky	3 to 56	100%	All places
Venonat	Walking in the overworld	7 to 12	100%	All places
Meowth	Walking in the overworld	7 to 12	100%	All places
Psyduck	Walking in the overworld	7 to 12	100%	All places
Bellsprout	Walking in the overworld	7 to 12	100%	All places
Tentacool	Surfing in the overworld	7 to 12	100%	All places
Tentacruel	Surfing in the overworld	7 to 12	100%	All places
Magikarp	Surfing in the overworld	7 to 12	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