Correspondence, manuscripts, documents, memorabilia, clippings, printed materials, and cassette tapes. Hammett's correspondence covers his retirement years, 1961-1986 and deals with translations and revised editions of his major works: Solutions of Electrolytes (1929), Physical Oraganic Chemistry (1940), and Introduction to the Study of Physical Chemistry (1952); congratulatory letters to Hammett upon his receiving various awards, including a letter from John F. Kennedy; congratulatory letters from Hammett to colleagues on their work; and correspondence with younger chemists about their research. Two letters from James B. Conant from 1947 constitute the only early correspondence. Manuscripts are comprised of Hammett's lectures and speeches given before meetings of scientists, 1961-1970; an oral history of Hammett by the American Institute of Physics (1978); papers given by various chemists at the Symposium on the History of Physical Organic Chemistry in 1983. There are also 10 cassette recordings of the above symposium.