Fonds consists of personal correspondence, newspaper clippings and manuscripts; as well as, memorial tributes, cards and letters of sympathy pertaining to the passing of Sonthoff. The fonds is arranged in the following series: Correspondence, Essays and Criticisms and Memorial Tributes.

This fonds primarily reflects Bartroli’s research interests in the early exploration and settlement of the Pacific Northwest by Spain. Research materials include annotated articles, notes, and article and book drafts on the early Spanish presence in B.C. Drafts and notes from his books and articles also involve research and writing on the Northwest Coast's early British voyages and occupations. Notes and drafts from his research and writing on the Spanish language and Sancho Panza from Don Quixote, are included.

This fonds also contains correspondence, programs, clippings from his speaking engagements, newsletters, and administrative records from his time as a member of El Circulo, UBC’s Spanish club.