The Continental Congress commissioned George Washington as Commander in Chief of the Continental Army on June 19, 1775. Washington was selected over other candidates such as John Hancock based on his previous military experience and the hope that a leader from Virginia could help unite the colonies.eorge Washington resigned his commission as Commander in Chief of the Continental Army in the senate chamber of the Maryland State House in Annapolis, where the Continental Congress was meeting on December 23, 1783. External Web Sites. George Washington's Resignation, Maryland State Archives.