The Manuscripts series consists of letters and documents primarily concerned with Pierre Samuel du Pont de Nemours, the Physiocrats, the French Revolution, and the antecedents of the Du Ponts and allied families in France. During the early 1920s, Pierre S. du Pont became an active collector of Du Pont materials, and bought several important bodies of manuscripts from French dealers. These materials were initially housed at his Longwood estate. In 1953, he chartered the Longwood Library, and when he died a year later, the library was incorporated as an independent research library. In 1961, the Longwood Library merged with the Hagley Museum.

This collection does not include materials that were passed to him by inheritance.

Of particular interest are letters from Jean Baptiste Colbert (1652), Gaspard de Coligny (1554), Jean Jacques Régis de Cambacérès (1795), and Comte Roger de Bussy-Rabutin (1675). Papers of Gabriel Denizot (1818) describe the establishment of the DuPont Powder Company at Eleutherian Mills. Also included are miscellaneous papers of Eleuthère Irénée du Pont. Papers of Francis Gurney du Pont (1850-1904) contain notebooks on explosions at the gunpowder mills (1815-1902). An autograph album of Union Civil War leaders, kept by William A. La Motte, an army officer of Wilmington, Delaware, includes one of the last signatures of Abraham Lincoln.

Papers collected by Philadelphia attorney Howard Potts include items relating to law enforcement in Philadelphia, with particular reference to the Olmstead Affair (1809). Also included is a letter of Tench Coxe concerning political affairs in Pennsylvania (1808), as well as other letters, pamphlets, and broadsides dealing with early nineteenth-century internal improvements and the promotion of agriculture. There is a rent roll for the colonial Manor of Moreland (Philadelphia County) in 1775. The collection contains a letter of George Washington to Irish political leader Sir Edward Newenham (1788). Also included are manuscript volumes entitled, "Etats de Franche Comté, 1606-1673." These are extracts made during the eighteenth century from Franc̜ois Nicholas Eugène Droz, "Recueil des édits, déclarations, lettres patents et arrêts du Conseil des Rois Louis XIV et Louis XV enregistrés en la Chambre des comptes, Cour des aides domaines et finances, ci-devant séante à Dole, et des règlemens de cette Cour depuis las réunion de las France-Commté à la Couronne" (Besanc̨on, 1778).

The Pierre Samuel du Pont de Nemours papers include a copy of his essay on education in the United States entitled, "Sur l'éducation nationale dans les Etats-Unis d'Amérique." He wrote the essay at the suggestion of Thomas Jefferson during the summer of 1800. Jefferson received the essay for correction and translation, but the process was never completed.