In 1930, Princeton University recruited Wigner and Von Neumann. When Adolf Hitler came to power in Germany in 1933, Wigner and von Neumann found safe haven in Princeton, New Jersey, though they still spent half the year in Europe, traveling, studying and teaching. In 1936, Wigner moved to the University of Wisconsin. On January 8, 1937, Wigner became a naturalized citizen of the United States. From 1938 until his retirement in 1971, Wigner was the Thomas D. Jones Professor of Mathematical Physics at Princeton University.
In 1939 and 1940, Dr. Wigner played a major role in agitating for a Manhattan Project, to build an atomic bomb. From 1942-1945, he worked on the Manhattan Project at the University of Chicago. Wigner was sorry to see atomic bombs dropped on Hiroshima and Nagasaki; nevertheless, he remained a defender of the U.S. military. Dr. Wigner always thought of his work on the atomic bomb as essentially defensive, and he would later become a major figure in the field of civil defense.
From 1946-1947, Wigner was appointed Director of Research and Development at Clinton Laboratories. From 1952-1957, he was a member of the General Advisory Committee to the U.S. Atomic Energy Commission.
He laid the foundation for the theory of symmetries in quantum mechanics. In the late 1930s, he extended his research into atomic nuclei. He developed an important general theory of nuclear reactions.
In 1963, Wigner received the Nobel Prize in Physics, along with Maria Goeppert-Mayer and J. Hans D. Jensen, for their contribution to the theory of the atomic nucleus and its particles. In addition to receiving the Nobel Prize, he was also been awarded the U.S. Medal for Merit (1946), Atoms for Peace Award (1960), the National Medal of Science (1969), and the Max Planck Medal of the German Physical Society. He was also a member of the American Physical Society and American Nuclear Society.
Wigner died on January 1, 1995, in Princeton.