Includes correspondence, clippings, photographs, financial records, typescripts of speeches and manuscripts (both published and unpublished), personal papers, astronomical and tree ring records, and related material pertaining to his work with Harvard College Observatory (1889-1894), Lowell Observatory, Flagstaff, Arizona (1894-1901), Steward Observatory, University of Arizona, Tucson (1918-1938), as well as his various positions as professor, dean, acting president, and first director of the Laboratory of Tree Ring Research at the University of Arizona. There is also material regarding his childhood; student days at Trinity College, Hartford (1885-1889); trips to South America (1890-1893), Mexico (1896-1897, 1923), and Europe (1910, 1912, 1930); his participation in civic and Masonic groups; the Carnegie Institution of Washington with which he was associated (1918-1938); various scientific meetings to which he contributed; and an unpublished biography by David F. Brinegar.