The James W.M. Harris Papers consist of over 200 letters written either from or to Harris or immediate members of his family between 1857 and 1909. The majority of the letters are from James to his wife Mary, written almost entirely during the Civil War. These letters contain descriptions of the siege of Vicksburg, life in Richmond, and first hand descriptions of African-Americans during the war. Harris also frequently recounts current events during the war, as well as encounters with Belle Boyd and Jefferson Davis. Other letters are from Mary to her husband relating day to day happenings, from various family members to other family, several letters from Harris to his daughters, a lengthy letter from Harris's mother describing conditions in Mississippi during the war, and finally condolence letters to James on the death of his wife.

Also contained in this collection are two ledgers of Mary Harris and Ann Lum listing household goods, details of plantation life including the shoe sizes of slaves, and remedies of illness. There are two photographs of Judge Harris and General Nathaniel Harris, and several more personal effects of the two gentlemen including a speech the judge gave to the Natchez Library Association and the documents of his bid for territorial Governor of Washington, and a casualty list for the Battle of the Wilderness for the general.