This series consists of correspondence sent to Carter H. Harrison III (1825-1893), Harrison's father. The subjects of the letters arranged in this series are varied. A number concern political matters, ranging from an explanation by Horace Boies, Governor of Iowa, of his positions on free coinage and trade, to requests by other Democratic politicians for promotions or jobs for their friends or constituents. Other letters are personal, such as thanks for his hospitality following visits, requests for meetings, letters of introduction, letters from his mother while he was at Yale, and letters from his wife. Also in this series is a letter from James S. Duff, who was in charge of the Chicago mayor's office during the administrations of John Rice and R. B. Mason, presenting Harrison's father with the keys to the old mayor's office that was destroyed during the Great Chicago Fire of 1871.

Certain of the items have handwritten annotations by Harrison explaining the context of the letter or providing some background material about the author, although far fewer of the letters in this series are annotated than in Series 2 (Incoming Correspondence).