These letters are addressed to S. J. Sedgwick and concern personal affairs, philology, scientific topics, publications, Afro-Americans, and gymnastics. There is also a letter to John L. LeConte discussing entomological subjects.

Principally letters from John Eatton LeConte, John Lawrence LeConte, Joseph LeConte, and Mrs. Jane LeConte Harden to Mrs. Matilda Jane Harden Stevens, Sumner Morrison Ramsey, Mrs. Ann LeConte Stevens, and Louis LeConte pertaining to family matters and natural history.

The approximately 3,700 color and black and white drawings were collected and drawn by John Lawrence LeConte, with two in the first volume are by Titian R. Peale, but most are likely by John Abbot. The previous description noted that there are some drawings by John Abbot, and that most were likely by John Lawrence Le Conte. However, John V. Calhoun has shown extensive evidence that most of the drawings are by John Abbot (John Abbot's "Lost" Drawings for John E. LeConte in the American Philosophical Society Library, Philadelphia. Journal of the Lepidopterists' Society 60(4), 2006, 211-217). The contents of the collection: 1. Coleoptera. 654 figures. 2. Diptera, Hemiptera, and Lepidoptera. 564 figures. 3. Coleoptera. 698 figures. 4. Coleoptera and Hymenoptera. 228 figures. 5. Coleoptera. 657 figures. 6. Hymenoptera and Diptera. 234 figures 7. Diptera. 304 figures. 8. Hemiptera, Araneina, Myripoda. 356 figures

These are primarily papers relating to the work of the United States Army Corps of Topographical Engineers, with special reference to surveys of harbors of the eastern United States. Some papers and letters relate to natural history and are addressed to John Lawrence LeConte. Correspondents include Rutherford B. Hayes, Joseph Henry, Daniel Parker, and E.G. Squier.

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.

A miscellaneous collection of letters written by naturalist Louis Jean Rodolph Agassiz concerning a wide range of topics: natural history and naturalists, geology, mineralogy, fossils, publications, expeditions, and the Museum of Comparative Zoology at Harvard, which he founded.

A product of the distinctive culture of reform in antebellum Philadelphia, William Parker Foulke was the scion of the old elite who put a conservative stamp on social change. Trained as an attorney, Foulke spent much of his adult life engaging his deep amateur interest in natural history and mental philosophy and devoting himself to a variety of civic and philanthropic causes, including the colonization of formerly enslaved persons, penal reform, and cultural institutions in his native Philadelphia. The Foulke Papers are the product of the diverse social and intellectual interests of the Philadelphia attorney and philanthropist William Parker Foulke. Consisting primarily of correspondence, notes, and essays, the collection touches on Foulke's many interests. The collection includes numerous lectures delivered by Foulke along with material on the Lancaster County Prison, New York Prison Association, and the Philadelphia Society For Alleviating the Miseries of Public Prisons; notebooks concerning prisons and prisoners, including a 1846-1852 diary, and a listing of prisoners, their race, age, crime, sentence, and observations; a diary concerning the American Colonization Society (1852); a copy of an arctic diary (1853-1854) by John Wall Wilson, in the hand of Isaac Israel Hayes, which recounts much of the journey aboard the brig Advance, commanded by Elisha Kent Kane. There is also a list of buildings (1820-1841) designed by John Haviland, and material on the American Academy of Music, Philadelphia.