The United States Bullion Depository at Fort Knox in Kentucky was built in 1936 as a heavily fortified inland repository for federal gold, moved from more vulnerable coastal cities. Operated by the U.S. Department of the Treasury, it became one of the nation’s principal gold storage sites, receiving enormous guarded shipments in 1937 and 1941 and helping establish Fort Knox as a byword for extreme security. During the Second World War it also protected foundational national documents and other treasures. Later used for additional government reserves and rare numismatic items, the depository was listed on the National Register of Historic Places in 1988 for its importance in American economic history.