The FBI was keeping tabs on the location of Japanese Nationals long before the start of World War II.
Before the start of World War II, more than a million Japanese were living abroad. Among them, some 112,418 lived in the United States. The FBI was concerned that among them were potential spies and saboteurs. The belief was rooted in the American experience during World War I when the Germans either dispatched spies and saboteurs to the United States or recruited German nationals or German-Americans for such clandestine operations.
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The full extent to which these maps were directly used once the US entered World War II in 1941 is unclear; however, they speak to the US Government’s long-running suspicions of the Japanese Empire at the time.
