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 Gates' mementoes related to his life's work and collection sales. Items span the years 1918 to 1940.

Contains notes in the form of notebooks and typescripts, compiled by Gates between the years 1898 and 1940, on both Mesoamerican and non-Mesoamerican languages, as well as geographical notes and calindrical studies.

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.