The Charles M. Byington diary contains approximately 95 pages of daily entries, covering January 1-July 19, 1863, and 5 pages of records documenting financial transactions. The earliest diary entries are quite brief and record daily activities, duties, and movements. Byington frequently noted that he had distributed equipment, made invoices, foraged for food to feed the soldiers, and drawn rations in his role as quarter-master sergeant. On January 4, 1863, he mentioned a soldier who had given religious instruction to an African American Regiment; in other entries he discussed the activities of his company's colonel, DeWitt Clinton Littlejohn, and those of several of his friends.
Byington wrote longer, more detailed entries beginning in March, when his regiment camped near Baton Rouge and he noted the frequent firing by gunboats there. On March 15, 1863, he gave a firsthand account of an engagement near Port Hudson, in which the USS Mississippi lost its rudder and exploded. In mid-April, he wrote about the Battle of Fort Bisland, including nearly getting hit by shells and seeing white flags hung outside of "most every house," reportedly by Confederate women frightened of the Yankees (April 19, 1863). In June, he described frequent foraging, his health problems, and the Battle of Port Hudson, in which several men he knew were wounded and killed (June 14, 1863). He also recounted a surprising assault by Confederate cavalry, which he and several officers fled by boarding a ship that was "peppered by bullets" (July 2, 1863). On July 18, 1863, he mentioned a visit to the decimated Port Hudson (July 14, 1863: "The buildings inside were literally torn to pieces"). The diary ends with a search for a coffin for "one of our boys" and a church visit on July 19, 1863.