Frank Siebert (1913-1998) is one of the key contributors to the field of Algonquian linguistics. While he did not pursue a degree in linguistics or anthropology, he independently acquired the skills and knowledge of a professional scholar. His work on Penobscot is some of the best and most comprehensive in existence. The Siebert Papers document the interest and work of Frank Siebert in the linguistics of the Algonquian family of languages, particularly Penobscot. The collection includes correspondence, research notes, drafts and published manuscripts by Siebert, as well as secondary sources consulted by Siebert. To a lesser extent, it contains material that documents Siebert's personal life, his interest in book collecting and his career as a physician.

The youngest son of Charles Willson Peale, Titian Ramsay Peale was an accomplished artist, naturalist, and explorer. This collection of ink, pencil, and watercolor sketches, with some engravings and lithographs, forms the bulk of Peale's artistic output. The drawings can be grouped into several periods of artistic output: pre-1818 (primarily watercolors of butterflies); from the Stephen Harriman Long Expedition to the American west in 1819-1820, on which Peale traveled as zoologist (there are views of animals, Indians, landscapes, etc.); for his 1821-1838 interlude period, spent primarily on the east coast (insects, animals, moose hunting in Marine, his trip to South America in 1830-1831, coin and medal designs); his period as a naturalist on the worldwide U.S. Exploring Expedition under the command of Charles Wilkes, 1838-1842; from the 1849-1873 period when he sketched around Washington, D. C. and in New Jersey; and there are more than 160 undated sketches of: animal skulls and bones, birds, plants, fish, insects, landscapes, and zoology.

Anthropologist and ethnographer Frank Gouldsmith Speck was one of Franz Boas' early graduate students and from 1907 till his death in 1950 spent his career in a variety of positions at the University of Pennsylvania, including its Museum of Archaeology and Anthropology. Unlike most of his contemporaries, Speck chose to study the cultures of Indigenous peoples of eastern North America, especially the Haudenosaunee, Cherokee, and peoples speaking Algonquian languages, such as Anishinaabe, Wabanaki, Innu, Lenape, and other Algonquian peoples within the eastern United States. Speck spent a larger amounnt of time in the field than was typical of most ethnographers, collecting documentary information and physical objects. The Frank G. Speck Papers consist of 15.5 linear feet of Speck's professional correspondence, field notes, lecture notes, and manuscripts of published and unpublished works. The material focuses on the Eastern Woodlands Indians, particularly the Catawba, Cherokee, Creek, Delaware, Houma, Haudenosaunee ("Iroquois"), Labrador Inuit ("Eskimo"), Innu ("Montagnais-Naskapi"), Nanticoke, Penobscot, Powhatan, Algonquian, and Yuchi. The collection is divided into two subcollections: Subcollection 1 is comprised of Speck's research material and correspondence, and Subcollection 2 consists of his manuscripts and related correspondence. The two subcollections were acquired separately by the Society, and were originally cataloged as the Frank G. Speck Papers (572.97 Sp3) and the Frank G. Speck Manuscripts on Native Americans (970.3 Sp3p) respectively.