Jonathan Williams, a nephew of Benjamin Franklin, was chief of the Corps of Engineers, United States Army, and first superintendent of the United States Military Academy at West Point. The genealogical material was "compiled from family records and his own personal knowledge by his son," H.J. Williams.

Three volumes contain letters, laws, charters, reports, proclamations, petitions, and other official and semi-official documents relating principally to early Pennsylvania and New Jersey, signed by or addressed to William Penn, among others. A fourth volume is Penn's cash book, 1699-1703, which records expeditures, payments of quit rents, etc. Tipped in is "Catalogue of Goods left at Pensbury," and of goods left at Philadelphia, 1701.