Twenty-two-year-old Fred Korematsu was parked on a San Francisco hillside with his girlfriend, listening to music on the car radio, when the broadcast stopped on Dec. 7, 1941. In the weeks that followed, the U.S. government imprisoned 120,000 people based solely on their ancestry. Fred, a California-born welder who had tried to register for the draft on the very first day he could, decided he wasn’t going anywhere. His decision would lead to one of the most consequential civil liberties cases in American history, and a decades-long effort to prove something that should never have needed proving.