Most letters are addressed to his wife and his son, George P. MacGowan, with some other correspondence as well. Other correspondents include Mrs. S. E. K. Ames, Rev. Cyrus Hamlin, and Mrs. George W. Hazel, who was MacGowan's sister-in-law. Letters from George P. MacGowan to George G. Heye, letter to George MacGowan from Paul D. Moody, President of Middlebury College, VT. Report of Operations by E. A. Carr at Fort Apache mentioning MacGowan's gallant acts. Telegram from E. A. Carr at Fort Apache to General Wilcox mentioning MacGowan's service. Most of the letters are postmarked from within the Arizona Territory or what is now Arizona. Many are from Fort Apache; some come from New Mexico, Idaho, and Wyoming, including San Pedro Crossing, Fort Barrett, Mimbres River, Turkey Creek Hill, La Mesilla, Goose Creek, and Cienega de Suez. Letters relate to the Indian Wars, describe the conditions of traveling to find Indians. Descriptions of the land and the wildlife include an account of finding an unknown species of diving bird. Later letters to George include college and life advice for him while he is a student at Middlebury College. Newspaper clipping of a news article about Camp Thomas and the Arizona Apache that mentions Captain MacGowan. The letters give detail on the fights between the troops and the Indians. Collection contains an index of the letters.