From the moment of Albert Einstein's arrival in the United States in l933, the year of the Nazis' ascent to power in Germany, until his death in l955, J. Edgar Hoover's FBI, assisted by several other federal agencies, began feverishly collecting "derogatory information" in an effort to undermine the renowned physicist's influence and destroy his reputation. Using material newly obtained through the Freedom of Information Act, Fred Jerome tells the story in depth of that anti-Einstein campaign, why and how the campaign originated, and provides the first detailed picture of Einstein's little-known political activism. The Einstein File not only reveals a little-known aspect of Einstein's considerable social and humanitarian concerns, but underscores the dangers that can arise to the American republic and the rule of law in times of obsession with national security.