George Washington's significant achievements in the founding of the United States include his role as the Commander-in-Chief of the Continental Army during the American Revolutionary War, where he led the colonies to victory against Britain. He presided over the Constitutional Convention in 1787, shaping the framework of the new government. Subsequently, as the first President of the United States, Washington established key precedents for the office, including the tradition of a two-term limit. His leadership and vision solidified the nation's democratic principles, earning him the title "Father of His Country."