Pokéfind

Route 1: Pidgey, Ratatta, Budew, Pikachu, Roaming Legendaries

Route 2: Pidgey, Rattata, Pikachu, Roaming Legendaries

Viridian Forest: Caterpie, Metapod, Weedle, Kakuna, Pikachu, Roaming Legendaries

Route 22: Nidoran♂, Nidoran♀, Mankey, Rattata, Heracross, Roaming Legendaries

Route 3: Pidgey, Mankey, Spearow, Ralts, Swablu, Roaming Legendaries

Mt. Moon: Zubat, Geodude, Paras, Aerodactyl, Clefairy, Kabuto, Cranidos, Roaming Legendaries

Route 4: Spearow, Sandshrew, Roaming Legendaries

Route 5: Meowth, Bellsprout, Oddish, Mankey, Roaming Legendaries

Route 6: Oddish, Pidgey, Rattata, Slowpoke, Meowth, Psyduck, Magnemite Roaming Legendaries

Route 11: Diglett, Slakoth, Sandshrew, Zangoose, Seviper, Snorlax, Dugtrio, Roaming Legendaries

Route 12: Poliwag, Krabby, Magikarp, Goldeen, Roaming Legendaries

PokemonTower: Ghastly, Misdreavus, Giritina, Cubone, Roaming Legendaries

Route 10: Magnemite, Voltorb, Onix, Machop, Nidoran♂, Nidoran♀, Murkrow, Shuppet, Zapdos, Roaming Legendaries

Route 7: Ekans, Pidgey, Roaming Legendaries

Route 8: Rattata, Sandshrew, Growlithe, Mankey, Roaming Legendaries

Route 16: Rattata, Doduo, Spearow, Fearow, Tropius, Grimer, Roaming Legendaries

Fuchsia City: Scyther, Tauros, Dratini, Dragonair, Tangela, Kangaskhan, Farfetch'd, Exeggcute, Nidorina, Nidorino, Chansey, Rhyhorn.

In front of Seafoam Cave: Articuno, Tentacool, Psyduck, Goldeen, Seel, Horsea, Larvesta (when you have been in there for a while), Roaming Legendaries

Route 19: 

Seafoam Cave: Lapras, Spheal, Seel, Snorunt, Zubat, Swinub, Sneasel, Roaming Legendaries

Route 17: 

Route 21: 

Cinnabar Volcano: Ryhorn, Dugtrio, Magmar, Moltres, Roaming Legendaries

Victory Road: Marowak, Machoke, Primeape, Starly (When you have been in there for a while.), Onix and roaming legendaries

Mysterious Grotto: Pichu, Roaming Legendaries

Elegant Valley: