The most counterfeited bill in the USA is the $20 bill, for it is not too suspicious and most nobody would take a second look. Next is the $100 bill, mainly counterfeited in other countries. 95% of all the new money being printed is used to replace U.S. dollars that wind up overseas. The U.S. Bureau of Engraving and Printing prints an average of 37 million bills a day. Most of the money printed is used to make up for currency already lost in circulation. The U.S. dollar is the most widely used currency in international transactions. All this printing requires 18 tons of ink per day. Thatâ€™s like 9 elephants. The paper and the ink currently used to print money is the exact same that was used during the Civil war and is not paper, but a cotton blend, but now it was changed so that it would last longer, and therefore doesnâ€™t have as much disease and stuff on it. Something about adding a slicker surface or something. Nine engravers produce all the plates, the planchets for currency, and all those plates are engraved in reverse. The U.S. Mint was the very first federal building built by the United States Government, and the coinage was struck using a decimal system created by Thomas Jefferson, who was the third president of the United States of America. The United State's largest mint is located in Philadelphia, which is the oldest being used, whose mintmark is either nonexistent or is a P. It covers over 5 acres. It was one of the few buildings that survived the great earthquake of 1906. Dollar bills are filthy, often turning up traces of Salmonella and E.coli. The older bills especially had more, because of the primarily cotton composition. The newer, slicker polymers had the least. In a study conducted by the University of Ballarat in Australia, scientist collected over 1,200 banknotes from various countries worldwide. The results showed that in the United States, the cleanest dollars hosted just 20 bugs, which the researchers refer to as a colony of forming units, or CFUs; the dirties dollars hosted well over 25,000. Most of the bacteria on the bills is completely harmless, but it is always a good idea to wash your hands after handling coinage or currency, especially if it is a lower denomination, for those usually have the most bugs.