In what year did the Star Spangled Banner become the official national anthem of the U.S. ?

I seem to remember, as a child, hearing that it was recognized as our National Anthem in 1931, but I will bow to your knowledge if I'm wrong, DG, since you are older and wiser and probably have a better recollection!

This being a Family site, I will refrain from editorial comment.
The song was made the official national anthem of the U.S. when President Herbert Hoover signed P.L. 823 on March 3, 1931.
Also see here for more details.