The plant physiologist and historian Rodney H. True (1866-1940) divided his career relatively evenly between the Bureau of Plant Industry in United States Department of Agriculture and the Department of Botany and Morris Arboretum of the University of Pennsylvania. A specialist in the physiological function of mineral nutrients in plants, True was active in his later career in the Philadelphia Society for Promoting Agriculture, the Pennsylvania Horticulture Society, and the Agricultural History Society. The True Papers consist of 6 linear feet of material relating primarily to the period of his career spent at the University of Pennsylvania. The collection contains roughly equal proportions of personal and professional correspondence, with a few diaries and research notebooks documenting his involvement with professional organizations and his interests in the history of his discipline.

The collection of Charles Coleman Sellers (1903-1980) contains copious and detailed documentation of the art of Charles Willson Peale and his family. It consists of working files for Sellers's numerous publications, including his Portraits and Miniatures by Charles Willson Peale (1952); Charles Willson Peale with Patron and Populace (1969); C. W. Peale's Portraits of Washington (1951); Benjamin Franklin in Portraiture (1962); Mr. Peale's Museum (1980). Most files include photographs of the art work, notes on the piece, and correspondence with authorities or owners. Other series include one relating to the paintings of various other Peales, including Anna C., James, Mary Jane, Raphaelle, Rembrandt, Rubens, and Sarah Miriam, and a miscellaneous artist file, which includes the same type of material and information on many eighteenth- and nineteenth-century artists, including Thomas Eakins, George Healy, Robert Edge Pine, William Rush, Thomas Sully, Benjamin West, James Abbott McNeill Whistler, etc. There is a separate Sellers collection at Dickinson College, primarily personal in nature.