Abstract The Thorn L. Mayes Sr. papers (1920s-1980s) consist of correspondence, maps, brochures, pamphlets, articles, field books, bulletins, and other materials concerning the exploration of canyon country in Utah and Arizona. A graduate of the University of California (1927), Thorn L. Mayes Sr. (1903-1987) was an electrical engineer who conducted geologic explorations of various areas in the western United States, such as Monument Valley.