The F.M. McMillen Diary was written by Sergeant McMillen while serving in Company C, 110th Ohio Volunteer Infantry, 2nd Brigade, 3rd Division, 6th Corps from January 1 - March 25, 1865. The diary records the activities of McMillen, who was mainly a clerk, as he participated in the Petersburg final assault during the Appomattox Campaign.
Entries of interest include descriptions of camp life, the growing number of Confederate desertions, the execution of a Union deserter and turncoat of the 1st Division (January 6, 1865), a Confederate raid after haversacks and overcoats (January 9, 1865), the execution of James Kelly of the 67th Pennsylvania Volunteers (March 11, 1865), a description of a chapel built near the Division Headquarters by the Engineer Corps (March 13, 1865) and the final days before the assault on Petersburg. Also included is a photocopy of the entry and exit holes in the diary made by a ball which could have taken McMillen's life.