Charles H. Mason (1886–1949) was employed for thirty-five years by Pierre S. "P.S." du Pont (1870-1954), the industrialist, entrepreneur, philanthropist, and horticulturalist who developed Longwood Gardens in Kennett Square, Pennsylvania. Mason worked as chief chauffeur and garage manager for du Pont. He lived with his family in a residence called "The Anvil" on the property at Longwood Gardens. This small collection includes Charles H. Mason and Marguerite Mason's journals (dictated by them and handwritten by Ann Mason, Charles Mason's sister) describing their early years in Lewes, Delaware.

Eleuthère Irénée du Pont (1771-1834) was the founder of E.I. du Pont de Nemours & Company. The collection contains original love letters from du Pont to his wife, Sophie (Dalmas) du Pont (1775-1828). He writes of how much he loves his wife and misses her when away. English transcribed extracts of several letters were done by their daughter, Sophie Madeleine du Pont (1810-1888).

Lavinia Dimmick (1874-1946) was a descendant of the founders of E.I. du Pont de Nemours & Company, a chemical research and manufacturing company. She was the daughter of Irene du Pont (1845-1877) and Edward Dimmick (1843-1895). Alfred Rée (1864-1933) was a chemist in England. This collection primarily consists of letters that passed between Alfred and Lavinia Rée during their courtship, ending with notes on their wedding reception, honeymoon travel and return to England.

William Gouverneur Ramsay (1866-1916) was a civil engineer for railroads and explosives corporations, including Repauno Chemical Company, Great Northern, and DuPont Company. His wife, Caroline “Lena” Johnston Canby (1872-1958) was interested in cultural and educational institutions and traveled extensively. The Ramsay family papers primarily consist of William G. Ramsay's personal and business papers, as well as his family's personal papers which primarily consist of correspondence, much of it between William Ramsay and Lena Ramsay prior to and after their marriage. the letters describe social life in Wilmington, literature, courtship and marriage, household administration, family life, child rearing and health.

Richard C. du Pont (1911-1943) was an aviator and businessman. In 1938, he purchaseds stock of an inactive company called All American Aviation, Inc. and became PresidentThis collection encompasses the time of Richard C. du Pont's marriage to his death, with a particular focus on his work with gliders. The establishment and growth of Summit Aviation, his son's private air transportation company, is heavily documented from the early 1960s onward. The majority of the collection consists of newspaper clippings and photographs.