Legal Tender Status Of Old Notes?

Indeed. The checkered history of the government's cancellation and resumption of "specie payments" (the convertibility of paper money to precious metal coins) during this nation's long history is a fascinating read in itself. The final slide into the abyss began with the Gold Reserve Act of 1933 (requiring everyone to turn in their gold coins and gold certificates under penalty of law!) and ended with a thud in 1965 with the start of the short redemption period for silver certificates.

Today, of course, our coins and paper money have no intrinsic value or backing, but it was not always so!