Canfield was the son of Augustus Cass Canfield (1854—1904), a wealthy engineer and yachtsman, and his wife, the former Josephine Houghteling. His stepfather was Frank Jay Griswold. He also was a great-grandson of Presidential candidate Lewis Cass. He had two sisters: Mary Cass Canfield and Laura Cass Canfield (Mrs William Lawrence Wood).
He attended the Groton School and Harvard University, graduating from Harvard in 1919 after serving as a lieutenant in the United States Army during World War I. Canfield also studied at New College, Oxford and trekked through Asia, retracing the route of Marco Polo.
After returning to New York, he worked as a reporter and advertising salesman for the New York Post. In 1924, he invested in Harper & Brothers and became manager of its London office. He held various executive positions with Harper's in London and New York between then and 1931; among the writers who he signed to Harper's contracts were James Thurber, E. B. White, J. B. Priestley, Harold Laski, John Gunther, and Julian Huxley. EM Delafield dedicated The Provincial Lady Goes Further to him.
Canfield was president of Harper & Brothers from 1931–45, board chairman from 1945–55, and chairman of the executive committee from 1955-67. From 1967 until his death in 1986, he was House Senior Editor at Harper's. He also wrote seven nonfiction books.
Government and political activities
During World War II, Canfield took a leave of absence from Harper's to serve as a member of the Board of Economic Warfare, the Foreign Economic Administration, and the United States Office of War Information. He was a founder of the journal Foreign Affairs.
Canfield campaigned for Adlai Stevenson in 1956. He was a strong supporter of birth control, served as chair of the executive committee of Planned Parenthood, and traveled extensively giving speeches and raising money to support the organization.
Canfield was thrice married.
He married his first wife, Katherine Temple Emmet, in 1922 and was divorced by her in June 1937 (she married, in October 1937, John D W Churchill). They had two sons: Michael Temple Canfield (1926–69, adopted), a London representative of Harper & Row; and Cass Canfield Jr., an executive at Harper & Row. According to the memoirs of Loelia, Duchess of Westminster, King Edward VIII of the United Kingdom believed that Michael Canfield was actually the biological son of his brother Prince George, Duke of Kent and socialite Kiki Preston; Michael became the first husband of Lee Radziwill.
Canfield's second wife was Jane Sage White, a sculptor, the former wife of Charles Fairchild Fuller, and a daughter of Ernest Ingersoll White. They married in 1938, and Jane Canfield died in 1984. By this marriage Canfield had three stepchildren: Jane Sage Fuller, Blair Fairchild Fuller, and Isabelle Whitney "Jill" Fuller.
In 1984, Canfield married Joan H. King.
- The Publishing Experience (1969)
- Up and Down and Around (1971)
- The Incredible Pierpont Morgan (1974)
- Samuel Adams' Revolution (1976)
- The Iron Will of Jefferson Davis (1978)
- Outrageous Fortunes: The Story of the Medici, the Rothschilds and J. Pierpont Morgan (1981)
- The Six (1983)
- The Provincial Lady Goes Further dedication page
- "Cass Canfield, A Titan of Publishing, Is Dead at 88", New York Times, March 28, 1986
- Cass Canfield, Dictionary of American Biography
- Michael T. Canfield obituary, New York Times, December 22, 1969
- Canfield/Emmet divorce notice, New York Times, June 10, 1937