One of the major reasons for the selection of George Washington as "commander-in-chief" came from his past. Washington had gained significant respect for his actions while serving in the French and Indian War. Upon arrival at the Second Continental Congress, Washington was appointed to a number of committees regarding the military.
Washington was also selected based on the fact that he was from Virginia. It was believed by a number of congressmen from the New England area, where much of the early fighting had occurred, that the leader of their forces should be someone from outside the area in order to create an actual Continental Army. They felt that appointing Washington to such a high position would also lead to greater involvement from Virginia, which at the time was the most populous colony, and also carried with it significant wealth.
Another motivating factor for Washington being appointed to the Continental Congress was his age and physical health. Washington, who was forty-three at the time, was young and healthy enough to be able to handle the physical demands of a military campaign. In addition, Washington's height and strong build made him an imposing figure who commanded respect.