This series consists mainly of unofficial records of Mary Virginia McCormick's physical and mental condition. The bulk of the material is letters written by different members of the household such as Miss Grace Walker and Dr. Alice Bennett to both Nettie Fowler McCormick and Cyrus H. McCormick, Jr. Included also are interviews with servants and other members of the household describing Mary Virginia's condition.

In addition to these unofficial reports, there are official medical reports such as that of 1889 which was used as evidence in the suit to declare Mary Virginia incompetent.

The three casebooks (vols. 1-3) describe the patient's day-to-day activities and reactions, and report on any significant changes in her condition.