Correspondence, diary (1865), journals (1850-1856), subject files, printed material, Langdon (Langston) family genealogical records, and other papers concerning Langdon's invention of card games (1846-1847), his work as professor of astronomy at Shelby College, Ky., and in the U.S. Patent Office (1851-1856), his long career as an Episcopal clergyman, his role in the founding of the Y.M.C.A. movement, especially in Washington, D.C., travels in Europe, Civil War, Clay-Webster debates, and the administrations of Millard Fillmore and Franklin Pierce. Correspondents include Langdon family members, A. D. Bache, Thomas Hart Benton, John C. Breckinridge, Phillips Brooks, Benjamin R. Curtis, George T. Curtis, George M. Dallas, Samuel Griswold Goodrich, Benjamin Apthorp Gould, Joseph Henry, Caroline Lee Hentz, Reverdy Johnson, Amos Kendall, Matthew F. Maury, Thaddeus Stevens, and George Ticknor.