To find new Pokémon, you need to pass through the streets of US cities a lot of miles. But often, these walks are vain.
Find rare Pokemon difficult, especially Pikachu. Common pokemons come across at every turn.
If you want to see the place where you can find rare Pokémon, you can use the maps that make Pokémon trainers.
Pokecrew - Crowdsourced Pokemon Go map
PokeMapper - Share and find #Pokemon
As a bonus list of rare Pokémon.
Everywhere:
Rattata, Pidgey, Weedle, Venonat, Zubat, Caterpie, Doduo,
Common:
Oddish, Paras, Gastly, Drowzee, Eevee, Magikarp, Meowth, Bellsprout, Ekans, Nidoran M/F, Polywag, Slowpoke, Goldeen, Krabby, Mankey,
Uncommon:
Spearow, Growlith, Jigglypuff, Cleafairy, Psyduck, Seel, Abra, Geodude, Sandshrew, Vulpix, Diglett, Exeggcute, Tentacool, Shellder, Onix,
Rare:
Machamp, Ponyta, Weezing, Voltrob, Horsea, Staryu, Tangela, Cubone, Ryhorn, Grimmer, Magnemite, Scyther, Lickitung,
Special:
Bulbasaur, Charmander, Squirtle, Pikachu, Omanyte, Kabuto, Aerodactyl, Hitmochan, Hitmonlee,
Epic:
Dratini, Farfetch'd, Mr.Mine, Jynx, Magmar, Electabuzz, Porygon,
Myths:
Lapras, Snorlax, Kangaskhan, Chansey