These papers consist chiefly of essays presented by the members, with such titles as "Ambition," "On Avarice," "State of Literature in the United States," and "Consequences of the French Revolution." Also included are several letters, including one from Benjamin Say, Jr.

This collection contains minutes of the Society, 1781-1975; minutes of the directors of the Corporation, 1929-1947; membership book (with signatures of early members), 1785; and names of later members. There are also deeds to the meeting house and burying ground; treasurers' accounts; reports of officers and committees; bills and receipts for constructing, maintaining, and repairing the meeting house; cancelled checks; and letters to the Society and its officers, especially Samuel Wetherill, 1883-1884.

A pioneer in ethnographic and linguistic studies of the American Indian and one of the most active members of the American Philosophical Society, Peter Stephen Du Ponceau helped to establish the American Philosophical Society's reputation as one of the world's foremost centers for the study of American Indians and their languages. The Peter Stephen Du Ponceau collection consists of correspondence on legal matters, Indian linguistics, silk culture, maritime law, the American Philosophical Society, and various publications of the early nineteenth century. The collection also includes several essays by Du Ponceau, most of which deal with maritime law.