Henry Clay Frick (1849-1919), a Pittsburgh industrialist who made his fortune in coke and steel, was also a prominent art collector. This series consists largely of Frick's incoming correspondence, with some outgoing letters, on matters relating to business and investments, art collecting, political activities, real estate, philanthropy, and family matters.

The Frick Collection's alphabetical subject files, 1932-1936, document the conversion of the New York residence of Henry Clay Frick to The Frick Collection, a public art museum, and the construction of a new Frick Art Reference Library building. Correspondence, internal memorandums, minutes, reports, clippings, inventories, and contracts detail the work of Organizing Director Frederick Mortimer Clapp; architect John Russell Pope; general contractor Marc Eidlitz; and Frick Collection Trustees, including Helen Clay Frick, Childs Frick and John D. Rockefeller, Jr.