31 U.S.C. §5103; 12 U.S.C. §411 ("The said notes shall be obligations of the United States and shall be receivable by all national and member banks and Federal Reserve banks and for all taxes, customs, and other public dues. They shall be redeemed in lawful money on demand at the Treasury Department of the United States, in the city of Washington, District of Columbia, or at any Federal Reserve bank.")