In Assassin's Creed III, George Washington leads the Continental Army during the American Revolution.
Washington appears as a major historical figure in the game's colonial American setting. The player character, Ratonhnhaké:ton, also known as Connor, encounters him while navigating the conflict between the Patriots, the British, and other factions. Washington's military leadership connects the fictional Assassin story to the real revolutionary campaign.
The Continental Army was created by the Second Continental Congress in 1775. Washington became its commander in chief and held that position through the Revolutionary War. Assassin's Creed III dramatizes his role, but the game's fictional conspiracy should not be treated as a literal account of American history.
Other famous figures, including Benjamin Franklin and Thomas Jefferson, are also associated with the era and appear in the broader historical context. They did not command the Continental Army, making Washington the specific answer to this question.