Gerard P. Kuiper (1905-1973) is considered by many as the father of modern planetary science. In 1960 Kuiper established the Lunar and Planetary Laboratory (LPL), first as part of the Institute of Atmospheric Physics and later as a separate unit at the University of Arizona. In his years at LPL Kuiper established a group of telescopes in the Santa Catalina Mountains above Tucson; made balloon spectroscopic observations of the Earth’s atmosphere; and conducted observatory site surveys in Hawaii, Mexico, and California. He also studied the atmosphere of Saturn’s moon Titan in 1944, the carbon dioxide atmosphere of Mars in 1948, Uranus’s satellite Miranda in 1948, and Neptune’s satellite Nereid in 1949. The Gerard P. Kuiper Papers are comprised of the personal and professional papers of astronomer Gerard P. Kuiper. The bulk of the material relates to his careers as an astronomical researcher and administrator at the Yerkes Observatory (University of Chicago), McDonald Observatory (University of Texas), and the Lunar Planetary Laboratory (University of Arizona). Items included in the collection are correspondence, publications, research material, newspaper clippings and photographs as well as Kuiper's personal experience as a member of the ALSOS Mission following World War II.