The Marshall Hilliard diary contains brief, near-daily entries covering January 11 to December 31, 1864, with the exception of January 26-March 3, 1864, for which the pages are missing. The bulk of the pocket-sized, 350-page diary documents Hilliard's experiences as a non-military prisoner of the Confederacy in Mississippi and Alabama, as well as his escape from prison at Meridian, Mississippi, and return home to Ohio. The diary opens with brief accounts of Hilliard's activities in the South prior to his capture, including letter writing, several financial transactions, and the arrival of his brother Frank's wife from Yazoo City, Mississippi (January 21, 1864). On January 23, l864, he wrote that he had been arrested near "the Fortifycations," but had eventually received permission to leave. At some point in the spring, likely during the late-winter period not covered by the diary, Confederates again arrested Hilliard and imprisoned him first at Yazoo City, where he was held until he could be transferred west by a steamship (March 17, 1864). He then spent time held in unnamed, likely makeshift prisons in Demopolis and Mobile, Alabama, and Meridian, Mississippi.
During his imprisonment in various locations in the Deep South, Hilliard frequently commented on the food he received and the general conditions in which he and his fellow prisoners lived. He and his friends frequently suffered from food poisoning due to the rottenness of the provisions they received. On May 27, 1864, in a typical entry, he wrote "We drew sour molasses for breakfast and they made me sick all day." On June 8, 1864, he noted that the prisoners had received "very bad beef for breakfast," but he had eaten a small enough amount of it that he avoided becoming sick. On many other days, Hilliard was not so lucky, as his frequent complaints of diarrhea and other digestive ailments bear out. Hilliard described the poor conditions in which he stayed, often noting that the rooms were dirty and cold. On March 15, 1864, he gave an account of staying in a large room with no fire: "Most all of the boys could not sleep at all and had to walk and dance to keep warm." He also remarked about traveling through the rough terrain, which he called worse than the pine woods of California (March 12, 1864).
Hilliard frequently expressed his belief that he would be exchanged soon, and the need became more urgent as he suffered increasing health problems in the spring of 1864. Eventually, he became too impatient to wait longer, and escaped on July 24, 1864, writing in his diary, "I broke out of Prison at Meridian Miss last night at 9 oclock…. We got out under the Posts." He then began a journey to the North that included such adventures as stealing chickens for sustenance (July 26, 1864) and escaping a pack of hounds (July 28, 1864). After more than a week as a fugitive, he encountered Union soldiers and took an oath of loyalty (August 5, 1864), eventually making his way north along water routes, which he described in several entries in August. The volume closes with Hilliard's return to ordinary civilian life, including social visits and church attendance.