Peter Stephen Duponceau, an American lawyer and scholar, born in the Isle of Re, France, June 3, 1760, died in Philadelphia, April 1, 1844. After studying at colleges in St. Jean d'Angely and Bressuire he went to Paris in 1775, and engaged in translating English books.

He was secretary to Baron Steuben, with whom he came to the United States, and on Feb. 18, 1778, was made captain by brevet in the American service. He accompanied Steuben in all his movements until the close of the campaign of 1779, when the army went into winter quarters in Philadelphia. Here Du-ponceau was threatened with a pulmonary disease, which for some time prevented him from performing active duty. Toward the close of 1780 he went with Steuben to the south, but renewed ill health forced him to return to Philadelphia early the next summer. Robert R. Livingston, secretary of foreign affairs, gave him a place in his office in October, 1781, which he held until June 4, 1783. He was admitted to the bar in Philadelphia in 1785, and acquired an extensive practice in the courts of Pennsylvania and also in those of the United States, including the supreme court. Jefferson tendered him the office of chief justice of Louisiana, which he declined. In addition to the duties of his profession he devoted much attention to philology. As chairman of the committee of history, moral science, and general literature of the American philosophical society, in 1819 he made a report on the "Structure of the Indian Languages," which at once gave him a high position in this department of knowledge.

In May, 1835, he received from the French institute, for a "Memoir on the Indian Languages of North America," the linguistic prize founded by the count de Volney. In 1838 he published "A Dissertation on the Nature and Character of the Chinese System of Writing," in which he held that the written language was lexigraphic, representing sounds and not ideas. He published several essays, letters, and reviews, and expended several thousand dollars, in an unsuccessful effort to introduce into the United States the production and manufacture of silk. His remaining writings comprise an extensive range of subjects; among which are original treatises on points of law; translations from the Latin, German, and French on similar subjects; various treatises on philology; and numerous contributions to American history, including a translation of "A Description of New Sweden," by Thomas Campanius Holm.