From the days predating the American Revolution, Downingtown has played a vital part in the development of not only Chester County but also the commonwealth of Pennsylvania and the United States of America. It was an important stop for farmers and tradesmen transporting goods between Lancaster and Philadelphia. During the Philadelphia campaign of the Revolution in 1777, the Continental Congress approved the storage of material for George Washington's army in Downingtown. Situated in the heart of one of William Penn's three original counties of Pennsylvania, the area grew into an important manufacturing community, known for its paper mills fueled by the east branch of the Brandywine River, which flows through the middle of the town.