Which U.S. General or Admiral had the most impact in the U.S. Military history? Why?

Answer 1

General George Washington, because he commanded the Continental Army which led to independendence from England and the founding of the U.S. Without Washington, there would be no U.S.

Answer 2

Technically, General Washington was not a US General, but rather a General of the Continental Army.

I would say the most influential was General U.S. Grant, without whom it is unsure if the U.S. and Confederate States would ever have been made to rejoin together.