Albert Einstein, the iconic German-born physicist and Nobel Prize winner visited the United States in 1933. During his visit, Adolf Hitler came to power so Einstein did not return to Europe. In this document dated January 15, 1936, Einstein filed his Declaration of intention to become and American Citizen, which he became in 1940. A few months prior, Einstein had written a letter to President Roosevelt alerting the President to the potential development of "extremely powerful bombs of a new type" and recommending that the U.S. begin nuclear research, which eventually led to the Manhattan Project. While Einstein supported the Allies during WWII, he was also vocal about the dangers of using nuclear weapons. Einstein worked at Princeton University until his death in 1955.