The most important manuscript collections for a biography of Salmon R Chase are those of the subject himself, especially the two large holdings at the Library of Congress and the Historical Society of Pennsylvania. Included here are vast amounts of incoming correspondence as well as numerous letters written by Chase, many of them found in letterbooks. Also included are financial and legal material, newspaper clippings, and speeches. The National Archives contains a great bulk of material related to Chase's direction of the Treasury Department. Among the hundreds of routine letters in the record groups of the Treasury Department and Civil War Special Agencies are occasional revealing Chase letters. Also important is the Port Royal Correspondence. The Ohio Historical Society includes a large collection relating to Chase's gubernatorial years. Smaller Chase collections are found at the Cincinnati Historical Society and the New Hampshire Historical Society. A major problem in each of these collections is Chase's abominable handwriting which worsened with time.
Other important Library of Congress collections include those of Abraham Lincoln, Andrew Johnson, John McLean, John Sherman, Martin Van Buren, Benjamin Wade, Jacob Schuckers, and Gideon Welles. Two significant Ohio collections are those of Joshua R. Giddings at the Ohio Historical Society and Alexander H. Long at the Cincinnati Historical Society.