It was 1933. America was descending into a depression. FDR issued Executive Order 6102:

"All persons are hereby required to deliver on or before May 1,
1933, to a Federal Reserve Bank or branch or agency thereof or
to any member bank of the Federal Reserve System all gold coin,
gold bullion and gold certificates now owned by them or coming
into their ownership . . .

"Whoever willfully violates any provision of this Executive Order . . .
may be fined not more than $10,000, or, if a natural person, may
be imprisoned for not more than ten years, or both . . ."

Note that the penalties were quite severe, and that all the gold was
literally to be turned over, not to the US Treasury, but to the private banking Federal Reserve System.

The plan was not rolled out because of an unexpected crisis. A full decade earlier, a new Federal Reserve Building was constructed, in 1923. In Cleveland. It was designed to contain the largest bank vault in the world and machine gun turrets on its exterior because it was to hold that confiscated gold.