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

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.

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.

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.