Final answer:
Joseph Brant, also known as Thayendanegea, was the Indian chief who fought for the British in New York and Pennsylvania during the American Revolution.
Step-by-step explanation:
The Indian chief who fought for the British in New York and Pennsylvania was Joseph Brant, also known as Thayendanegea. He rose to prominence while fighting for the British during the American Revolution and joined forces with Colonel Barry St. Leger during the 1777 campaign. After the war, Brant moved to the Six Nations reserve in Canada and continued to resist White encroachment onto Native lands.