This collection includes correspondence of William E. Lingelbach, briefs, news accounts, etc., concerning the Clark documents that had belonged to General John Hammond and which were turned over to the Minnesota Historical Society in 1953, resulting in litigation concerning ownership.

This collection contains correspondence, research notes, papers and addresses, memoranda, drafts of letters and papers. These items center on Lingelbach's career at the University of Pennsylvania and at the American Philosophical Society. There is much correspondence with noted historians relating to various topics. His interest in political history and foreign policy, and his participation in national organizations can be seen in such files as the Foreign Policy Association, National Resources Planning Board, and the U.S. War Dept. Committee on Education and Special Training (World War I).

Founded in 1743 by Benjamin Franklin, the American Philosophical Society was the first learned society in the United States. For over 250 years, the Society has played an important role in American cultural and intellectual life. Until the mid-nineteenth century, the Society fulfilled the role of a national academy of science, national library and museum, and even patent office. Early members of the Society included Thomas Jefferson, David Rittenhouse, Benjamin Rush, Stephen Peter Du Ponceau, George Washington, and many other figures prominent in American history. The Archives of the American Philosophical Society consists of 192.25 linear feet of material, organized into thirteen record groups dating back to 1743. The Society's archives extensively documents not only the organization's historical development but also its role in American history and the history of science and technology.