Contains photocopies, notes, and typescripts, compiled by Gates between 1898 and 1940, of source materials in the Huastec language.

Contains photocopies, typescripts, manuscripts, and notes of texts collected by Gates in various Mesoamerican languages.

Contains writings related to Gates' institutional affiliations with the Aryan Theosophical Society, the San Diego Museum, and the Department of Middle American Research at Tulane University. While his work with the Department of Middle American Research at Tulane University was directly related to the study of Mesoamerica, Gates' affiliations with the Aryan Theosophical Society and the San Diego Museum were not related to the study of Mesoamerica.

Contains notes on Mesoamerican astrology and calindrics compiled by Gates between the years 1898 and 1940.

Contains selected writings of Gates prior to 1930, including notes, printed studies and articles, and public addresses. All items pertain to the study of Mesoamerica, with the exception of an article on the conditions in post-revolution Mexico and an article on Chinese art.

Contains notes, reports, and other materials related to Gates' work with the Department of Middle American Research at Tulane University. Includes information on the history and archaeology of Guatemala, as well as to the contemporary situation in the region. Most prevalent are documents relating to Tulane's 1925 agricultural survey of the Southern Mexican state of Tabasco. Materials date from between approximately 1920 and 1926.

Contains administrative notes relating to the Aryan Theosophical Society branch in Point Loma, California, as well as one set of notes on the Society's study of Isis Unveiled. Gates' involvement with the Aryan Theosophical Society lasted from the 1905 until the years following the First World War.