William du Pont, Sr. (1855-1928) was an industrialist and member of the prominent du Pont family of Delaware, whose family business was the E.I. du Pont de Nemours & Company, also known as the DuPont Company which was a large manufacturer of gunpowder. He worked for the first DuPont dynamite manufacturer, Repauno Chemical Company, as secretary and treasurer (1880-1884) and after the tragic death of Lammot du Pont (1831-1884), as president (1884-1892). William du Pont, Jr. was the youngest child of du Pont, Sr. and Annie Rogers Zinn du Pont (1858-1827). Du Pont Jr. became the president of Delaware Trust Company in 1929, the youngest bank president in Wilmington at that time. In 1952, he became chairman of the board, retaining both positions until his death in 1965. The William du Pont family papers are organized into two record groups: William du Pont, Sr. papers and William du Pont, Jr. papers. The William du Pont, Sr. papers primarily encompass the years of his active business life from the early 1880s to his death in 1928. There are also some papers from his early life and after his death. The William du Pont, Jr. papers document areas of his activities predominantly concerned with land development in Wilmington, Delaware; farming, animal breeding and foxhunting in Delaware, Pennsylvania, Maryland and Virginia; and promotion of horse racing in the United States, especially in Delaware.