An archaeological anthropologist and linguist, John Alden Mason spent the majority of his career at the University Museum of the University of Pennsylvania. After receiving his undergraduate degree at Penn in 1907, Mason received a doctorate at Berkeley (1911) for his ethnographic work on the Salinan Indians of California, but his diverse interests in later years ran the gamut from Puerto Rican folklore to Piman languages and cultures (including Pima, Papago, Pima Bajo, Northern and Southern Tepehuan, and Tepecano), Mayan, Aztec, and Incan archaeology, and the languages of South American Indians. Mason was curator of the University Museum at Penn from 1926 until his retirement in 1958. The Mason Papers include both in-coming and outgoing correspondence, linguistic material, notes, and photographs relating to Mason's work in the southwestern U.S., northern Mexico, and South America. Centered on the years after Mason's return to Philadelphia in 1926, the collection covers all aspects of Mason's professional life, from reports on field work to answering casual questions referred to him through the University Museum to data and analyses on Piman and other languages. The collection also contains voluminous files relating to the Mason's editorship of the American Anthropologist (bulk: 1945-1948). Of special note are a series of class notes (1908-1910) kept by Mason for course work in ethnology, archaeology, and linguistics at the University of Pennsylvania under Edward Sapir and Frank Speck.