United States Notes (characterized by a red seal and serial number), originally issued in 1862, were the first National currency. Federal Reserve Notes were not issued until the creation of the Federal Reserve System in 1913. Both types of notes were redeemable in gold until 1933, when the United States abandoned the gold standard. Since then, both currencies have served essentially the same purpose, and have had the same value. Because United States Notes serve no function that is not already adequately served by Federal Reserve Notes, their issuance was discontinued, and none have been placed into circulation since January 21, 1971.
All outstanding United States Notes, which were issued in denominations of $1, $2, $5, $10, $20, $50, $100, $500, and $1,000, may be redeemed at face value by the U.S. Treasury Department. Payment would be made in the form of a Treasury check.
You may purchase United States Notes from numismatic dealers who are likely to be found online. Also, publications for money collectors such as Bank Note Reporter and Coin World routinely display advertisements of currencies for sale. These publications may be found at most reputable newsstands, book stores, and libraries.