James Watson and Francis Crick announce to friends that they have determined the chemical structure of DNA; the formal announcement takes place on April 25 following publication in April's Nature (pub. April 2).
Cold War: U.S. President Dwight D. Eisenhower formally approves the top secret document National Security Council Paper No. 162/2, which states that the United States' arsenal of nuclear weapons must be maintained and expanded to counter the communist threat.