Part 2: Beat Brock — Pewter City Gym, badge 1

Beat Brock — Pewter City Gym, badge 1 opens 15 areas. There are 78 trainers standing in them. The fights at this checkpoint are Rival Blue (Bulbasaur), Rival Blue (Charmander), Rival Blue (Squirtle), and 1 more.

Where to go

1. Mt. Moon

   Wild: Paras 100% · Lv 5-10, Zubat 69% · Lv 7-10, Geodude 30% · Lv 9-10, Clefairy 6% · Lv 10-12

   Trainers: Bug Catcher Kent Lv 11, Bug Catcher Robby Lv 10, Hiker Marcos Lv 10, Lass Iris Lv 14, Lass Miriam Lv 11, Super Nerd Jovan Lv 11 +6 more

   Pick up: TM46 Thief

2. S.S. Anne

   Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 60% · Lv 5-15, Krabby 60% · Lv 5-15 +5 more

   Trainers: ★ Rival Blue (Bulbasaur) Lv 20, ★ Rival Blue (Charmander) Lv 20, ★ Rival Blue (Squirtle) Lv 20, Fisherman Barny Lv 17, Fisherman Dale Lv 17, Gentleman Arthur Lv 19 +13 more

   Pick up: TM44 Rest, HM01 Cut

3. Diglett's Cave

   Wild: Diglett 95% · Lv 15-22, Dugtrio 5% · Lv 29-31

4. Route 3

   Wild: Spearow 35% · Lv 6-8, Pidgey 30% · Lv 6-7, Nidoran♀ 14% · Lv 6-7, Nidoran♂ 14% · Lv 6-7 +3 more

   Trainers: Bug Catcher Colton Lv 10, Bug Catcher Greg Lv 9, Bug Catcher James Lv 11, Lass Janice Lv 9, Lass Robin Lv 14, Lass Sally Lv 10 +2 more

5. Route 4

   Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 84% · Lv 15-35, Krabby 84% · Lv 15-35 +8 more

   Trainers: Lass Crissy Lv 31

   Pick up: TM05 Roar

6. Route 5

   Wild: Pidgey 40% · Lv 13-16, Meowth 35% · Lv 10-16, Bellsprout 25% · Lv 13-16, Oddish 25% · Lv 13-16

7. Route 6

   Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Slowpoke 100% · Lv 20-40, Poliwag 60% · Lv 5-15 +7 more

   Trainers: Bug Catcher Elijah Lv 20, Bug Catcher Keigo Lv 16, Camper Jeff Lv 16, Camper Ricky Lv 20, Picnicker Isabelle Lv 16, Picnicker Nancy Lv 16

8. Route 11

   Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 84% · Lv 15-35, Krabby 84% · Lv 15-35 +9 more

   Trainers: Engineer Bernie Lv 18, Engineer Braxton Lv 21, Gamer Darian Lv 18, Gamer Dirk Lv 18, Gamer Hugo Lv 18, Gamer Jasper Lv 18 +4 more

9. Route 23

   Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Slowpoke 100% · Lv 20-40, Poliwag 60% · Lv 5-15 +11 more

10. Route 24

    Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 84% · Lv 15-35, Krabby 84% · Lv 15-35 +11 more

    Trainers: Bug Catcher Cale Lv 10, Camper Ethan Lv 18, Camper Shane Lv 14, Lass Ali Lv 12, Lass Reli Lv 16, Team Rocket Grunt Lv 15 +1 more

    Pick up: TM45 Attract

11. Route 25

    Wild: Magikarp 100% · Lv 5, Psyduck 100% · Lv 20-40, Slowpoke 100% · Lv 20-40, Poliwag 60% · Lv 5-15 +11 more

    Trainers: Camper Flint Lv 14, Hiker Franklin Lv 15, Hiker Nob Lv 13, Hiker Wayne Lv 17, Lass Haley Lv 13, Picnicker Kelsey Lv 15 +3 more

    Pick up: TM43 Secret Power

12. Cerulean City

    Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 84% · Lv 15-35, Krabby 84% · Lv 15-35 +4 more

    Trainers: ★ Rival Blue (Bulbasaur) Lv 18, ★ Rival Blue (Charmander) Lv 18, ★ Rival Blue (Squirtle) Lv 18, Team Rocket Grunt Lv 17

    Pick up: TM03 Water Pulse, TM28 Dig

13. Vermilion City

    Wild: Magikarp 100% · Lv 5, Tentacool 100% · Lv 5-40, Horsea 60% · Lv 5-15, Krabby 60% · Lv 5-15 +6 more

    Pick up: TM34 Shock Wave

14. Kanto Underground Path

    Wild: Nidoran♀ Lv 5-100, Nidoran♂ Lv 5-100

15. Pewter City Gym

    Trainers: ★ Brock Lv 14, Camper Liam Lv 11

★ Rival Blue (Bulbasaur) — Cerulean City

4 Pokémon · level cap Lv 18 (every cap) · Rival Blue (Bulbasaur)’s own page

	Pokémon	Ability & item	Moves	Base stats
	Pidgeotto Lv 17 NormalFlying		Tackle Sand Attack Gust Quick Attack	HP63Attack60Defense55Sp. Atk50Sp. Def50Speed71Total349
	Abra Lv 16 Psychic		Teleport	HP25Attack20Defense15Sp. Atk105Sp. Def55Speed90Total310
	Rattata Lv 15 Normal		Tackle Tail Whip Quick Attack	HP30Attack56Defense35Sp. Atk25Sp. Def35Speed72Total253
	Bulbasaur Lv 18 GrassPoison	Ability Overgrow	Sleep Powder Poison Powder Vine Whip Leech Seed	HP45Attack49Defense49Sp. Atk65Sp. Def65Speed45Total318

★ Rival Blue (Charmander) — Cerulean City

4 Pokémon · level cap Lv 18 (every cap) · Rival Blue (Charmander)’s own page

	Pokémon	Ability & item	Moves	Base stats
	Pidgeotto Lv 17 NormalFlying		Tackle Sand Attack Gust Quick Attack	HP63Attack60Defense55Sp. Atk50Sp. Def50Speed71Total349
	Abra Lv 16 Psychic		Teleport	HP25Attack20Defense15Sp. Atk105Sp. Def55Speed90Total310
	Rattata Lv 15 Normal		Tackle Tail Whip Quick Attack	HP30Attack56Defense35Sp. Atk25Sp. Def35Speed72Total253
	Charmander Lv 18 Fire	Ability Blaze	Metal Claw Ember Growl Scratch	HP39Attack52Defense43Sp. Atk60Sp. Def50Speed65Total309

★ Rival Blue (Squirtle) — Cerulean City

4 Pokémon · level cap Lv 18 (every cap) · Rival Blue (Squirtle)’s own page

	Pokémon	Ability & item	Moves	Base stats
	Pidgeotto Lv 17 NormalFlying		Tackle Sand Attack Gust Quick Attack	HP63Attack60Defense55Sp. Atk50Sp. Def50Speed71Total349
	Abra Lv 16 Psychic		Teleport	HP25Attack20Defense15Sp. Atk105Sp. Def55Speed90Total310
	Rattata Lv 15 Normal		Tackle Tail Whip Quick Attack	HP30Attack56Defense35Sp. Atk25Sp. Def35Speed72Total253
	Squirtle Lv 18 Water	Ability Torrent	Tackle Tail Whip Withdraw Water Gun	HP44Attack48Defense65Sp. Atk50Sp. Def64Speed43Total314

Also fought around here

Everything you can have caught by this checkpoint · Open the interactive guide

It also doesn't say when 4 of its areas open up, so they are listed together in the last part rather than guessed into the story.