The Breton collection consists of photocopies of 100 letters addressed to Ella Lewis of Philadelphia, Adela C. Breton's friend and relative. Purely personal in nature, 94 of these were written by Breton, and 6 (all written after her death) by her brother Harry, and although they offer little insight into Breton's archaeological or artistic interests, they do provide a glimpse of her personality and her opinions on everything from American immigration law to the First World War, the malice of Germans, and her experiences traveling in western Canada.