After a brief career in the Congregational church, J. Peter Lesley (1819-1903) left the ministry in 1852 to work full-time as a geologist. Having gained experience in structural geology and stratigraphy with the First Pennsylvania Geological Survey (1836-1842), Lesley became an expert in the geology of coal, working for the Pennsylvania Railroad and other corporations and conducting some of the first systematic studies of the state's hydrocarbon resources. A long-time professor at the University of Pennsylvania, he was elected to the APS in 1856, serving variously as its librarian, secretary, and vice president, and he was selected as Director of the Second Pennsylvania Geological Survey (1875-1889). The Lesley Papers include letters to and from Peter Lesley and his wife, Susan on geology, coal and iron mining, abolition, educational reform, organized charity, and Unitarianism. The collection offers important insight into academic and applied geology in late 19th century Pennsylvania, the development of the coal and iron industries, as well as into the Lesleys' progressive social and intellectual milieu. It is divided into three series: Lesley's general correspondence, his correspondence with his brother Joseph, and microfilms of Lesley's research notes.

For many years referred to as the "Franz Boas Collection of American Indian Linguistics," this collection consists of a large body of linguistic and ethnographic material gathered together by Boas and many of his colleagues and students primarily from the 1890s to the 1940s. It contains the bulk of Boas's own fieldwork material, with the main exception of most of his Inuit and earliest Northwest Coast fieldwork. It contains the majority of the work sponsored by American Council of Learned Societies Committee on Native American Languages, which was directed by Franz Boas, Edward Sapir, Alfred Kroeber, and other academic linguists from 1927-1937. The collection, however, also contains related kinds of fieldwork and derived secondary materials created outside the auspices of this Committee, both earlier and later. The first deposit of the material arrivied in 1945. Subsequently, additional related materials were donated and added, as noted in the listings. Additionally, the documentary materials produced by some of the early projects (1945 to circa 1955) of the APS Phillips Fund for Native American Research were added to this collection. The collection has grown to over 80 linear feet of material representing at least 166 languages and dialects from the United States, Canada, and Mexico. The formats range from field notes and ethnographic texts to slip files, vocabularies, lexica, and grammars, and dozens of linguists and Native consultants are represented.

The Papers of Curt Stern include extensive correspondence, lectures (1920s-1970s, 1.5 boxes), autobiographical material, articles, zoological course notes, photographs, etc. Stern's various areas of scientific interest are documented in the collection: the chromosome theory of heredity, role of gene mutation and chromosome rearrangements in evolution, action and interaction of genes during individual development, and particularly his contribution to the development of human genetics as a discipline (centered on his popular and influential book, Principles of Human Genetics, 1949, 1960, 1973). Both his career in Germany and the United States is documented in his correspondence. After studying with T. H. Morgan at Columbia University on a Rockefeller Foundation Fellowship (1924-1926), Stern returned to Richard Goldschmidt's lab at the Kaiser-Wilhelm Institute (1926-1932). There is material of note in the collection concerning this period when Stern helped to establish the cytological basis of crossing over. After a short stay at the California Institute of Technology in 1932, Stern's temporary residence in the U. S. became permanent, and his later career at the University of Rochester, 1933-1947 (Chairman, Department of Zoology) and at the University of California, Berkeley, 1947-1970 (there is abundant material on the Department of Zoology) is covered in the collection. There is other material on: American Association for the Advancement of Science Inter-Society Committee on Science Foundation Legislation, 1946-1947; American Society of Human Genetics (Pres., 1957); Atomic Energy Commission (Advisory Committee for Biology and Medicine, 1950-1955); Genetics (journal); Oak Ridge National Laboratory (Advisory Committee for Biology, 1955-1968); and the Rockefeller Foundation. Stern's correspondence with friends and colleagues in Germany, England, and the U. S., during the 1920s-1930s, is of particular note as it documents not only the developments in genetics and the institutional and administrative networks supporting research, but it also offers general comments and observations on science, Germany, and politics. The photographs (2 boxes) include pictures of many prominent geneticists and scientists.