Several reports covering the scientific work of the expedition were made, and most were published. One of the exceptions was the ichthyology report, which Charles Pickering was originally assigned to prepare. It was delayed, however; and by the middle of 1849, Jean Louis Agassiz had been placed in charge of the work. Due to the pressures of his many other commitments, and to the growing reluctance of Congress to appropriate additional funds after 1862, Agassiz never completed the project. In 1885, twelve years after Agassiz's death, the fish specimens, his manuscript, and its illustrations were sent to the United States National Museum.|The two illustrators, Joseph Drayton and Alfred T. Agate, produced numerous drawings of fishes during the expedition, many of which are in this collection. Drayton also helped supervise the illustrations and engraving work for a number of the scientific reports which were published.|A number of the items covering the ichthyology of the United States Exploring Expedition have been held, along with the specimens, by the Division of Fishes of the United States National Museum of Natural History. This record unit includes an unsigned manuscript on the fishes of the expedition, apparently the work of Jean Louis Agassiz which was sent to the United States National Museum in 1885; notes on the fishes and echinoderms collected by the expedition, either by Charles Pickering or based on his notes; a number of items concerning the drawings, specimens and the itinerary of the expedition; and drawings and illustrations of fishes done during the voyage or as illustrations for the ichthyology report. An unpublished manuscript on the fishes of the United States Exploring Expedition by Henry Ward Fowler has been placed in RU 7180.|In addition to the ichthyological materials some items in this collection were held by the Smithsonian Library. These items consist of a letter from R. R. Waldron to Mrs. Sarah Jane Hale concerning her son Horatio Hale's travel plan, 1841; a manuscript on the expedition by Titian Ramsay Peale, which was published by the American Historical Records, 1874; notebooks on botany, mostly by William Dunlop Brackenridge; catalogues and annotated lists of ethnological, geological, mineralogical, and natural history specimens collected by the expedition; drawings of echinoderms by Drayton; original invoices and other official papers of the expedition, mostly shipping lists of specimens sent to the United States; and some loose sheets from the purser's account book, 1838-1842.