This series contains an assortment of letters that were apparently neither written by, nor sent to, Harrison or his family. It is not clear why Harrison kept many of the letters in this series, or even how he obtained them in the first place. Some may have been collected because Harrison felt that the author was a person of historical significance, such as the letters written by William Jennings Bryan and the note written by Oliver Wendell Holmes, others may have been forwarded to Harrison by the addressee. Some of the letters refer to Harrison's father or other members of his family. The letter from A. S. Trude, for example, relates to Patrick Eugene Prendergast, the man who murdered Carter H. Harrison III.