The Cohen family collection contains correspondence between several family members regarding several topics including civil rights, genealogy, and Fort McHenry. The materials in the collection are dated from 1818 to 1945.

This collection contains the correspondence of Dr. John Hanson Thomas sent during his imprisonment during the Civil War. Dr. Thomas and his wife, Annie Campbell Thomas, née Gordon, wrote each other almost every day during his time as a prisoner of war from September 1861 to February 1862, and letters between the couple make up the majority of the collection. These letters discuss daily life in the prison camp, political views, current events, and family matters.