Greetings:

Since the $100,000 notes were never in circulation, they are not collectible. By the way, they were Gold Certificates, not Federal Reserve Notes. According to the most recent records, only about 106 $5,000 notes and about 170 $10,000 notes of all varieties have not yet been redeemed. A number of them are in museums or institutional reference collections, and are thus not available to private collectors.

Joe is right that the Bureau of Engraving and Printing (a division of the Treasury Department) produces all U.S. paper money. However, it only sells currently produced currency to the public. Collectors can buy other currency from dealers such as The Currency House, from dealers at coin and currency shows, or through Internet auctions sites such as EBay.

As I said before, $500 and $1,000 notes are expensive, but most are not rare. Depending upon series, signature combination, and condition, you can find them for a little over two times their face value. You can even buy ones that are torn, scuffed, have had adhesive tape removed, or are otherwise undesirable for a small premium over face value.

During the American Civil War and for about a decade thereafter, there was also paper currency circulating in denominations under one dollar: 3¢, 5¢, 10¢, 15¢, 25¢, and 50¢. Some series of this Fractional Currency were issued by the Treasury Department, but some were issued by the Post Office Department. The latter were called Postage Currency, and were redeemable in postage stamps rather than in coins.

One last thing: those portraits cited above refer only to the small size U.S. currency, first produced in 1928 and released for circulation early in 1929. Many different designs and portraits were used on the large size currency produced from 1861 to 1928.

--- Steve