Meriwether Lewis and William Clark were explorers. This collection contains the manuscript journals kept by Lewis and Clark on their travels to the source of the Missouri River and across the continent to the Pacific Ocean. There are interlineations throughout by Nicholas Biddle, who published his narrative "History of the Expedition of Captains Lewis and Clark" (1814).

George Ord made important contributions as an ornithologist and writer but is also famous for his contempt of fellow ornithologist John James Audubon. Throughout his life he published numerous scientific articles and assisted in completing Alexander Wilson's life's work, American Ornithology; or, The Natural History of the Birds of the United States. Ord also left his mark as a member of the American Philosophical Society and as the president of the Academy of Natural Science of Philadelphia. The George Ord collection consists primarily of outgoing personal correspondence to Charles Waterton ranging from 1831 to 1866 that highlights Ord's professional as well as personal affairs, most notably his hostility toward Audubon. The collection is supplemented by correspondence of Ord's to and from various individuals regarding personal and business matters.