This collection includes letters, manuscript and typescript drafts of his publications. They relate to his works Fighting the Insects: the Story of an Entomologist (1933); and with Harrison D. Dyar and Frederick Knab, A Monograph of the Culicidae of North and Central America. The latter is one volume of the larger three-volume published work The Mosquitoes of North and Central America and the West Indies (1912).

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.