This collection of personal papers include materials gathered by McNary on the treatment and exchange of Union prisoners during the Civil War. There are several manuscript accounts of prison life submitted to McNary by members of the National Association of Union Ex-Prisoners of War, for which McNary was historian. He also served as the Kansas state vice-president for the Association in the late 1880s. In addition, there is family correspondence, a genealogy, clippings, and six photographs of McNary in his military uniform and other members of the McNary family.

The collection is arranged in one box as follows: Correspondence, 1853-1895, undated; Documents, Prisoner of War narratives (alphabetical); Family correspondence (1890-1932); Genealogy and other materials (1803-1955). Photographs have been physically separated and are located at RH MS-P 42; two diaries kept by McNary during and directly after his time as a prisoner of war are located at RH MS A9.

Correspondents in the collection include Thomas H. Copern, John P. Coore, Jesse Hawes, William Kelley, Jr., W.P. McClure, B.C. McWilliams, C.D. Nichols, T.J. Pattee, Hueston Smith, and J.C. Wagoner.