The largest city of Delaware, on the Delaware River southwest of Philadelphia, Pennsylvania. It was founded as Fort Christina by Swedish settlers in 1638 and held by the Dutch from 1655 until 1664, when it was taken by the English. E.I. Du Pont built a powder mill nearby in 1802, which established Wilmington's chemical industry. Following the liberalization of Delaware's banking laws in the 1980s, the city became a center of the credit card industry.