The photos below give us a fascinating look inside the FBI’s filing system during the Second World War. Housed in the Washington, D.C. Armory, the FBI’s archive collected more than 23 million cards and over 10 million fingerprint records, with around 400,000 new cards added monthly.

Take a closer look.

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES

During WWII, the federal government invested a large amount of resources to investigate potential defectors and spies.

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES

By the end of 1943, the FBI have employed around 13,000 people.

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Since 1924, the FBI has been the sole U.S. repository for fingerprints.

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES

GEORGE SKADDING/THE LIFE PICTURE COLLECTION/GETTY IMAGES