Horatio Allen (1802-1889) was a noted civil engineer and inventor, who worked with the Delaware & Hudson Canal Company, the South Carolina Canal and Railroad Company, the Croton Aqueduct, and the New York & Erie Railroad. The bulk of his the papers is personal correspondence (1818-1864), and biographical materials collected by his family. Also included is a small collection of Allen's business papers, particularly concerning his work on the New York & Erie Railroad.