After the mint closed, it performed a variety of functions for the Federal government. It was first downgraded to an assay office for the U.S. Treasury as it had been from 1876 to 1879. Then, in 1932, the assay office closed and the building was converted into a Federal prison, in which capacity it served until 1943. The Coast Guard then took over the building as a nominal storage facility, though in truth the structure was largely abandoned and left to decay until it was transferred to the state of Louisiana in 1965. During the Cold War, when many believed there to be a high risk of nuclear war, the old Mint was considered to be the best fallout shelter in the city.