On the Border with Crook is considered one of the best firsthand accounts of frontier army life, as the author of the book gives equal time to both the soldier and the Native American. John Bourke, the author of this book was a captain in the United States Army. He served as an aide to General George Crook in the Apache Wars from 1872 to 1883. As Crook's aide, Bourke had the opportunity to witness every facet of life in the Old West—the battles, wildlife, the internal squabbling among the military, the Indian Agency, settlers, and Native Americans. Bourke kept a diary in sequential journals throughout his adult life, documenting his observations in the West. He used these notes as the basis for his later monographs and writings. During his time as aide to General Crook during the Apache Wars, Bourke kept journals of his observations that resulted in this book. Within it, Bourke describes the landscape, Army life on long campaigns, and his observations of the Native Americans. His passages recounts General Crook's meetings with Sitting Bull, Crazy Horse, and Geronimo as the General attempted to sign peace treaties and relocate tribes to reservations. Bourke provides considerable detail of towns and their citizens in the Southwest, specifically the Arizona Territory.