Executive Order 9066, signed by President Roosevelt on February 19, 1942, authorized the military to exclude "any or all persons" from the West Coast — in practice, the removal and incarceration of some 120,000 people of Japanese ancestry, two-thirds of them American citizens, without charge, hearing, or individual suspicion. Families were given days to dispose of homes and businesses, held in converted racetracks and fairgrounds, then shipped to ten War Relocation Authority camps in desert and swampland, behind barbed wire and under gun towers, for the better part of four years.

The government's own intelligence had found no basis for mass removal, a fact its lawyers concealed from the Supreme Court. Within the camps, dissenters — those who answered the loyalty questionnaire "no-no," protested conditions, or resisted the draft — were segregated at Tule Lake or imprisoned again in Justice Department internment camps, prisoners within the prison. Congress formally apologized in the Civil Liberties Act of 1988, acknowledging that the incarceration arose from "race prejudice, war hysteria, and a failure of political leadership" — the largest single act of political imprisonment in American history.