Go east of Cinnabar Island to the Seafoam Islands.
The third gym leader is Whitney.
A Magmar level 54, a Macargo level 54, and a Rapidash level 59.
you must frist go to seafoam island where blaine is, he is the 15th gym leader, then go to cinnibar island and a character who is behind the Pokemon center will then say that he is the last gym leader, once you have talked to him he will go to viridian city gym, he is the last gym leader. this is for heartgold and soulsilver :) hope this helped.
The final gym is the Viridian City Gym. Blue is the Gym leader.
Gym Leader Blue
Not enough info: which gym leader?
You CAN NOT become a Gym Leader in Pokemon HeartGold and SoulSilver or ANY MAIN SERIES POKEMON GAME.
It's near the Seafoam Islands.
In the goldenrod gym.
You can battle all of the gym leaders out of order in the Kanto Region. Thus, the perspective of the 15th gym leader will change from person to person. Chronologically, Blaine is the 15th gym leader, and he is in the Seafoam Islands, and is up the first ladder you see when you enter.
Brock.
beat gym leader