The papers of Henry Harrison Barnard consist of four modest file units, which primarily document his experiences during the 1860s. His personal correspondence with his family, friends, and future wife, Clarissa Pomeroy, make up the bulk of his collection.

Barnard's letters to Clarissa (1861-62) express his confidence in a short war, the inefficient postal system, the prevalence of sickness—particularly typhoid fever—in the ranks, and every soldier's desire for long and numerous letters. They also allude to a budding romance between the correspondents.

Barnard's letters to his family and friends are only a little more comprehensive, covering the date span of 1861-66. Included are details covering the events after his discharge from the Army (1864). He wrote his friend, Valney McRoberts, of his journey to Alabama and the beginning of his employment on a Southern plantation (1865). Barnard's letters also document the names of the men in his company, the troubles of writing while at war, the rumors and stories heard around camp, and his own adventures on the march and on the battlefield.

The collection also contains a folder of letters written by people other than Barnard. Although these letters do not directly involve Barnard, their date span (1837-66) places the majority of them in antebellum times. Thus, they may provide additional insights into the causes of the Civil War. Of special interest, this folder contains a letter from Alonzo Barnard, a missionary among the Minnesotan Chippewa, to his niece and Barnard's sister, Abby L. Barnard (1858). This letter, which describes a trip from Belle Prairie to Lake Winnipeg in a horse-drawn sled, caught the attention of the Minnesota Historical Society, which published the find in Minnesota History (March 1934).

In addition to letters, Barnard's collection contains miscellaneous newspaper clippings and receipts. A copy of "Genealogy of the Wood Family" is included; its connection with Barnard comes through his paternal grandmother, whose maiden name was Wood. Finally, the collection contains the commission from Acting Postmaster General Alexander Rundall (1866), which secured Barnard the position of postmaster of Cuba Station, Alabama.