This collection contains mostly entomological material, with much information on the description and identification of particular insects, entomological collections, and the study of entomology in Europe and the United States. In addition, there are materials on medicine and hospitals during the American Civil War, on the Corps of Topographical Engineers, the United States Army, on natural history in the United States, and on the LeConte's family. Some letters are written to President Rutherford B. Hayes and concern the Commissionership of Agriculture, for which LeConte was considered, but not appointed. Letters of John Eatton LeConte and Joseph LeConte are included.

In addition to family and business correspondence, the Charles Nicoll Bancker Family Papers contains various documents, such as a furniture inventory volume (30pp.); a Daybook, 1795-1800 (120pp.); and a very interesting journal (unidentified, but by one of the Banckers, and filed under "Description of a trip..."), from New York to Albany and back, between July 20-Aug. 15, 1793 (1 vol., 31 pp.). It contains detailed observations of the Hudson River and the towns along the way. Bancker was involved in business and trade prior to 1826, and in insurance after that date, so there is material relating to those topics in this collection. He owned a substantial library of the period, which was used by Charles Wilkes's Expedition after 1837 (see Reynell Coates to Bancker). This library, along with Bancker's notable scientific instrument collection, was sold after his death and there are published auction catalogues in the collection. There is much family correspondence from: Anne E. Bancker, Charles Gerard Bancker, Evert Bancker, Sarah U. Bancker, Violetta Bancker Talbot, Elizabeth Bancker Teackle, and John Teackle.

A physician, natural historian, and professor at the University of Pennsylvania, Benjamin Smith Barton (1766-1815) was one of the central figures in Philadelphia's early national scientific establishment. Having received his medical training in European universities, Barton was appointed Professor at the University of Pennsylvania in 1789, lecturing on botany, materia medica, natural history. A prolific author, he established his reputation as one of the nation's preeminent botanists through his botanical text book The Elements of Botany (1803), but his contribtions to zoology, ethnology, and medicine were equally noteworthy. Barton's monograph on the "fascinating faculty" of the rattlesnake and his efforts in historical linguistics (New Views of the Origin of the Tribes and Nations of America, 1798) were widely read, and his Philadelphia Medical and Physical Journal (1804-1809) was one of the nation's first medical journals and an important outlet for natural historical research. The Barton Papers offer a comprehensive view of the professional work of Benjamin Smith Barton from the time of his return to the United States in 1789 until his death. The collection is divided into five series: Correspondence, Subject Files, Bound Volumes, Graphic Materials, and Printing Plates. The collection includes a particularly valuable series of botanical, medical, and natural historical drawings collected by Barton for research, reference, and publication. Among the many artists represented are William Bartram, Frederick Pursh, Pierre Turpin, and Benjamin Henry Latrobe.