before 1929 you could trade in your banknotes for their value in gold or silver, the note will usually say below the portrait "THIS NOTE IS LEGAL TENDER FOR ALL DEBTS, PUBLIC AND PRIVATE, AND IS REDEEMABLE IN LAWFUL MONEY AT THE UNITED STATES TREASURY OR ANY FEDERAL RESERVE BANK." but after the depression, the federal reserve revoked that after the depression.
Btw we should make silver coins of Trump and use those as currency lol