The correct answer is D) it was on a river.
The reason that made Philadelphia a great area for factories and trade was that it was on a river.
The city of Philadelphia is located along the Delaware River and Schuylkill River, in the greater Delaware Valley. English Quaker William Penn founded the city in 1682. Since the beginning, Philadelphia was a social center for the colonies that based an important part of its economy on trade with the big advantage that was located next to the river and had ports. That is why many factories were located there. Philadelphia used to trade lumber, coal, furs, textiles, and bricks.