The Pennsylvania National Guard is one of the oldest and largest National Guards in the United States Department of Defense. It traces its roots to 1747 when Benjamin Franklin established the Associators in Philadelphia. With more than 18,000 personnel, the Pennsylvania National Guard is the second-largest of all the state National Guards. It has the second-largest Army National Guard and the fourth-largest Air National Guard. These forces are respective components of the United States Army and Air Force.