Primarily correspondence with some speeches, reports, and other material relating to McCulloch's career as a banker and financier, as U.S. comptroller of the currency (1863-1865), and as U.S. secretary of the treasury (1865-1869 and 1884-1885). Subjects include enfranchisement of African Americans, currency, national debt, finance, politics, Reconstruction, and tariff. Correspondents include Edward Atkinson, James Gillespie Blaine, George S. Boutwell, William E. Chandler, Salmon P. Chase, Schuyler Colfax, Samuel Sullivan Cox, William Pitt Fessenden, John Murray Forbes, Morris Ketchum, Joseph Medill, John Sherman, John Aikman Stewart, Charles Sumner, and Robert C. Winthrop.